update_not_possible message

### Is there an existing issue for this?

- [X] I have searched the existing issues

### Package ecosystem

pub

### Package manager version

_No response_

### Language version

3.1.5

### Manifest location and content before the Dependabot update

./pubspec.yaml

### dependabot.yml content
```
---
job:
package-manager: pub
source:
provider: github
repo: orgName/repoName
directory: "/."
branch: fix-dependabot
api-endpoint: https://api.github.com/
hostname: github.com
credentials:
- type: pub_repository
url: https://xxxxx
token: xxxx
```
### Updated dependency

I have the same problem with several dependencies both internal and external. This is an example of an internal one:
pubspec.yaml:
name: "my_home"
version: ^2.2.0

pubspec.lock version 2.2.0

### What you expected to see, versus what you actually saw

What happens: the module(s) are not updated
what I would expect: this module gets updated to 2.4.0

I see the log message "Requirements to unlock update_not_possible" but it is not clear for me why it is not possible to update. I could not find any docs on this warning and I also could not find a way to further debug the issue.

### Native package manager behavior

when running "flutter pub upgrade my_home" the module get's updated to 2.4.0

### Images of the diff or a link to the PR, issue, or logs

updater | 2024/01/26 09:03:37 INFO Checking if my_home 2.2.0 needs updating
updater | 2024/01/26 09:03:37 INFO Latest version is 2.4.0
updater | 2024/01/26 09:03:37 INFO Requirements to unlock update_not_possible
updater | 2024/01/26 09:03:37 INFO Requirements update strategy
updater | 2024/01/26 09:03:37 INFO No update possible for my_home 2.2.0

### Smallest manifest that reproduces the issue

_No response_

Start with the pubspec.yaml, pubspec.lock, and dependabot.yml details, then compare the logged update_not_possible result with running "flutter pub upgrade my_home". Trace how the pub updater evaluates the 2.2.0 to 2.4.0 update and use the logs to identify why Dependabot rejects it. Done means the cause is explained and the dependency can be updated or the limitation is documented.

Written by the indexing model from the issue text.