Unable to resize gcp disk through google.cloud.gcp_compute_disk

##### SUMMARY
I am unable to resize the disk size through google.cloud.gcp_compute_disk.
The initial value for the disk size does not get updated to the new value

```
- hosts: localhost
tasks:
- name: create a disk
google.cloud.gcp_compute_disk:
name: test-disk
size_gb: 30
state: present
project: "{{ gcp_project }}"
auth_kind: "{{ gcp_creds_type }}"
service_account_contents: "{{ gcp_creds }}"
zone: "{{ gcp_zone }}"

- name: resize the disk
google.cloud.gcp_compute_disk:
name: test-disk
size_gb: 60
state: present
project: "{{ gcp_project }}"
auth_kind: "{{ gcp_creds_type }}"
service_account_contents: "{{ gcp_creds }}"
zone: "{{ gcp_zone }}"
```

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
google.cloud.gcp_compute_disk.

##### ANSIBLE VERSION
```
ansible [core 2.11.6]
config file = /var/home/automate/eddie/infra-ansible-linux/ansible.cfg
configured module search path = ['/home/automate/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
ansible python module location = /home/automate/.local/lib/python3.8/site-packages/ansible
ansible collection location = /home/automate/.ansible/collections:/usr/share/ansible/collections
executable location = /home/automate/.local/bin/ansible
python version = 3.8.10 (default, Mar 15 2022, 12:22:08) [GCC 9.4.0]
jinja version = 3.0.2
libyaml = True
```

##### COLLECTION VERSION

```paste below
# /home/automate/.ansible/collections/ansible_collections
Collection Version
----------------- -------
community.general 2.5.1

# /home/automate/.local/lib/python3.8/site-packages/ansible_collections
Collection Version
----------------- -------
community.general 3.8.1
```

##### CONFIGURATION

```paste below
DEFAULT_HOST_LIST(/var/home/automate/eddie/infra-ansible-linux/ansible.cfg) = ['/var/home/automate/eddie/infra-ansible-linux/inventory']
DEFAULT_ROLES_PATH(/var/home/automate/eddie/infra-ansible-linux/ansible.cfg) = ['/var/home/automate/eddie/infra-ansible-linux/roles', '/home/automate/.ansible/roles', '/var/home/automate/eddie/shared/roles']
DEFAULT_TIMEOUT(/var/home/automate/eddie/infra-ansible-linux/ansible.cfg) = 30
DEPRECATION_WARNINGS(/var/home/automate/eddie/infra-ansible-linux/ansible.cfg) = False
INVENTORY_IGNORE_EXTS(/var/home/automate/eddie/infra-ansible-linux/ansible.cfg) = ['~', '.orig', '.bak', '.cfg', '.retry', '.pyc', '.pyo']
```

##### OS / ENVIRONMENT

Ubuntu 20.04.4 LTS

##### STEPS TO REPRODUCE

```yaml
- hosts: localhost
tasks:
- name: create a disk
google.cloud.gcp_compute_disk:
name: test-disk
size_gb: 30
state: present
project: "{{ gcp_project }}"
auth_kind: "{{ gcp_creds_type }}"
service_account_contents: "{{ gcp_creds }}"
zone: "{{ gcp_zone }}"

- name: resize the disk
google.cloud.gcp_compute_disk:
name: test-disk
size_gb: 60
state: present
project: "{{ gcp_project }}"
auth_kind: "{{ gcp_creds_type }}"
service_account_contents: "{{ gcp_creds }}"
zone: "{{ gcp_zone }}"
```

##### EXPECTED RESULTS

It should resize the disk to the new value

##### ACTUAL RESULTS

It does not resize the disk to the new value.

```paste below
PLAY [localhost] ************************************************************************************************************************************************************************************************

TASK [Gathering Facts] ******************************************************************************************************************************************************************************************
ok: [localhost]

TASK [create a disk] ********************************************************************************************************************************************************************************************
changed: [localhost]

TASK [resize the disk] ******************************************************************************************************************************************************************************************
changed: [localhost]

PLAY RECAP ******************************************************************************************************************************************************************************************************
localhost : ok=3 changed=2 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
```

Start by locating the google.cloud.gcp_compute_disk module and trace how it handles an existing disk when size_gb changes. Reproduce the two-task playbook with a 30 GB disk followed by 60 GB, then verify that the second task actually resizes the disk and reports the correct result.

Written by the indexing model from the issue text.