Use the javaversion constant instead of string.

[rlazo]

This is compatible with the way it's done in all other projects.

https://github.com/firebase/firebase-android-sdk/search?p=1&q=targetCompatibility&unscoped_q=targetCompatibility

[google-oss-bot]

Binary Size Report

Affected SDKs

• transport-api

  Type	Base (43f5c6d)	Head (3272c15d)	Diff
  apk (aggressive)	11.0 kB	11.0 kB	+6 B (+0.1%)
  apk (debug)	23.0 kB	23.0 kB	+15 B (+0.1%)

• transport-runtime

  Type	Base (43f5c6d)	Head (3272c15d)	Diff
  apk (aggressive)	35.6 kB	35.6 kB	-17 B (-0.0%)
  apk (debug)	80.6 kB	80.6 kB	-24 B (-0.0%)

Test Logs

• Base (43f5c6d8): https://android-ci.firebaseopensource.com/view/gcs/android-ci/logs/postsubmit-binary-size/1272546379482271746
• Head (3272c15d): https://android-ci.firebaseopensource.com/view/gcs/android-ci/pr-logs/pull/firebase_firebase-android-sdk/1673/binary-size/1273286920918536192

Notes

Head commit (3272c15d) is created by Prow via merging commits: 43f5c6d 30d1bc5.

[google-oss-bot]

Coverage Report

Affected SDKs

No changes between base commit (43f5c6d) and head commit (3272c15d).

Test Logs

• Base (43f5c6d8): https://android-ci.firebaseopensource.com/view/gcs/android-ci/logs/postsubmit-check-coverage/1272546379482271745
• Head (3272c15d): https://android-ci.firebaseopensource.com/view/gcs/android-ci/pr-logs/pull/firebase_firebase-android-sdk/1673/check-coverage-changed/1273286920918536195

Notes

HTML coverage reports can be produced locally with ./gradlew <product>:checkCoverage.
Report files are located at <product-build-dir>/reports/jacoco/.

Head commit (3272c15d) is created by Prow via merging commits: 43f5c6d 30d1bc5.