Bot message changes for -f and rebase (#106150)
* Encourage people to use -i instead of -f for mergebot
* Add additional info for when rebase fails due to lacking permissions
<details><summary>dryrun</summary>
````
csl@csl-mbp ~/zzzzzzzz/pytorch [csl/errormsgs] $
(forpytorch) python3 .github/scripts/tryrebase.py 106089 --branch viable/strict --dry-run
+ git -C /Users/csl/zzzzzzzz/pytorch rev-parse --verify refs/remotes/origin/viable/strict
@pytorchbot started a rebase job onto [refs/remotes/origin/viable/strict](https://github.com/pytorch/pytorch/commit/7c97c943fbba4f6a58698aaa4312fcf4123a36cc). Check the current status [here](None)
+ git -C /Users/csl/zzzzzzzz/pytorch fetch origin pull/106089/head:pull/106089/head
+ git -C /Users/csl/zzzzzzzz/pytorch rebase refs/remotes/origin/viable/strict pull/106089/head
+ git -C /Users/csl/zzzzzzzz/pytorch rev-parse --verify pull/106089/head
+ git -C /Users/csl/zzzzzzzz/pytorch rev-parse --verify refs/remotes/origin/viable/strict
+ git -C /Users/csl/zzzzzzzz/pytorch push --dry-run -f https://github.com/Lightning-Sandbox/pytorch.git pull/106089/head:fix/spaces
stdout:
remote: Permission to Lightning-Sandbox/pytorch.git denied to clee2000.
fatal: unable to access 'https://github.com/Lightning-Sandbox/pytorch.git/': The requested URL returned error: 403
stderr:
Rebase failed due to Command `git -C /Users/csl/zzzzzzzz/pytorch push --dry-run -f https://github.com/Lightning-Sandbox/pytorch.git pull/106089/head:fix/spaces` returned non-zero exit code 128
```
remote: Permission to Lightning-Sandbox/pytorch.git denied to clee2000.
fatal: unable to access 'https://github.com/Lightning-Sandbox/pytorch.git/': The requested URL returned error: 403
```
This is likely because the author did not allow edits from maintainers on the PR or because the repo has additional permissions settings that mergebot does not qualify.
````
</details>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/106150
Approved by: https://github.com/huydhn