chore(ci): remove firestore project and its reference

[iyabchen]

remove firestore project and its reference
hashicorp/terraform-provider-google#17775

Release Note Template for Downstream PRs (will be copied)

[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes:

Diff report

Your PR generated some diffs in downstreams - here they are.

google provider: Diff ( 5 files changed, 3 insertions(+), 37 deletions(-))
google-beta provider: Diff ( 1 file changed, 11 deletions(-))
terraform-google-conversion: Diff ( 1 file changed, 7 deletions(-))

[modular-magician]

Tests analytics

Total tests: 3620
Passed tests: 3255
Skipped tests: 365
Affected tests: 0

Click here to see the affected service packages

all service packages are affected

$\textcolor{green}{\textsf{All tests passed!}}$
View the build log

[SarahFrench]

Approved the TeamCity-related changes. The changes make sense looking at them, the TeamCity tests are passing, and if I run some Firestore tests with in the current TeamCity setup with the environment variable set to a nonsense variable I can see that acc tests pass

[roaks3]

Fly-by comment: it looks like the prior usage was removed here #10168