Fix repo-scripts test case failing due to incorrect name

[dlarocque]

The tests in repo-scripts/prune-dts read all *.input.d.ts and try to read the corresponding *.output.d.ts files with the same name.
This causes a test case to fail because there is a file named resolves-generics-through-inheritance.input.d.ts, but the corresponding output file is incorrectly named resolves-generics-through-inheritence.index.d.ts (inheritence, not inheritance), so there's an error when we try to read the file:

1 failing

  1) Prune DTS
       resolves generics through inheritance:
     Error: ENOENT: no such file or directory, open '/Users/dlarocque/workspace/firebase-js-sdk/repo-scripts/prune-dts/tests/resolves-generics-through-inheritance.output.d.ts'

[changeset-bot]

⚠️ No Changeset found

Latest commit: 33ed6d8

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[google-oss-bot]

Size Report ¹

Affected Products

No changes between base commit (2561b63) and merge commit (cf2fec6).

Test Logs

• Base (2561b63): https://github.com/firebase/firebase-js-sdk/actions/runs/10929067925
• Merge (cf2fec6): https://github.com/firebase/firebase-js-sdk/actions/runs/10963815530

1. https://storage.googleapis.com/firebase-sdk-metric-reports/Ljs6TOoink.html

[google-oss-bot]

Size Analysis Report ¹

Affected Products

No changes between base commit (2561b63) and merge commit (cf2fec6).

Test Logs

• Base (2561b63): https://github.com/firebase/firebase-js-sdk/actions/runs/10929067925
• Merge (cf2fec6): https://github.com/firebase/firebase-js-sdk/actions/runs/10963815530

1. https://storage.googleapis.com/firebase-sdk-metric-reports/wnqV7pkSNu.html