Bump libraries-bom from 20.9.0 to 25.2.0

[KDB223]

Updating BOM version to prevent googleapis/java-firestore#822 from occurring when using Admin API instead of Firestore API directly. 20.9.0 uses an old version of Firestore which does not contain googleapis/java-firestore#834.

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[felipebonezi]

Updating BOM version to prevent googleapis/java-firestore#822 from occurring when using Admin API instead of Firestore API directly. 20.9.0 uses an old version of Firestore which does not contain googleapis/java-firestore#834.

Do you need help to get this PR merged?

[lahirumaramba]

Hi, we can't upgrade the libraries-bom without dropping support for Java 8, which we have planned to do in the next major release. I have already started the process and will use #678 to track the progress.