Unfreeze firestore python generation

### Determine this is the right repository - [x] I determined this is the correct repository in which to report this bug. ### Summary of the issue Firestore generation was skipped in https://github.com/googleapis/google-cloud-python/pull/17413 because the firestore changes broke system tests. Needs to be unskipped by removing this line: https://github.com/googleapis/google-cloud-python/blob/2e75c78cdd09d4472ed412a2e925196effaea9fd/librarian.yaml#L1154 ### API client name and version _No response_ ### Reproduction steps: code file: main.py ```python def reproduce(): # complete code here ``` <any additional py files> ### Reproduction steps: supporting files file: mydata.csv ``` alpha,1,3 beta,2,5 ``` <any additional supporting files> ### Reproduction steps: actual results file: output.txtmydata.csv ``` Calculated: foo ``` ### Reproduction steps: expected results file: output.txtmydata.csv ``` Calculated: bar ``` ### OS & version + platform _No response_ ### Python environment _No response_ ### Python dependencies _No response_ ### Additional context _No response_