"A pull request already exists" is output even if there is no PR

[koppor]

In case the action could create a branch, but not a PR and is run a second time, the output is

A pull request already exists that updates Gradle Wrapper to 9.2.0.

This is wrong.

Quick fix. Replace by:

There is already a branch existing that updates Gradle Wrapper to 9.2.0.

This covers both the branch and the PR.

Alternatively, there could be a check for a PR opened. If PR exists: Output PR message, if no PR, output branch message.

[huehnerlady]

And if the branch exists but no PR is opened it would be good to open the PR :)