Deleting a task with a project changes IDs immediately

## To report a bug...

### What command(s) did you run?
```shell
❯ export TASKDATA=test
❯ task add project:test test1
TASKDATA override: /home/janek/test
Created task 1.
The project 'test' has changed. Project 'test' is 0% complete (1 task remaining).
❯ task add test2
TASKDATA override: /home/janek/test
Created task 2.
❯ task 1 delete
Delete task 1 'test1'? (yes/no) y
Deleting task 1 'test1'.
Deleted 1 task.
TASKDATA override: /home/janek/test
The project 'test' has changed. Project 'test' is 0% complete (0 of 0 tasks remaining).
❯ task 2 done
TASKDATA override: /home/janek/test
No tasks specified.
```
### What did you expect to happen?
Deleting the first task shouldn't change the id of the second as specified in https://taskwarrior.org/docs/ids.html
### What actually happened?
The id of task "test2" immediately changed to 1 after the deletion. This only happens if the deleted task is part of a project.
### Paste the output of the ```task diag``` command.
```
task 2.5.1
Platform: Linux

Compiler
Version: 7.5.0
Caps: +stdc +stdc_hosted +LP64 +c8 +i32 +l64 +vp64 +time_t64
Compliance: C++11

Build Features
Built: Apr 6 2020 16:03:00
Commit: 64243e6ec
CMake: 3.15.3
libuuid: libuuid + uuid_unparse_lower
libgnutls: 3.5.18
Build type: release
```