ci: release-type should be read by release-please-config (#2432)

* ci: use java-backport in Release Please branches

java-lts release type was outdated (go/backport-releases#2-run-the-release-brancher-cli-tool).
It created a strange pull request with "-sp.1" suffix version.

* ci: release-type should be read by release-please-config

Author: suztomo

.github/release-please.yml

@@ -1,22 +1,15 @@
 handleGHRelease: true
 manifest: true
-releaseType: java-yoshi
 branches:
   - bumpMinorPreMajor: true
     handleGHRelease: true
-    releaseType: java-lts
     branch: 9.0.x-lts
   - bumpMinorPreMajor: true
     handleGHRelease: true
-    releaseType: java-lts
     branch: 8.0.x-lts
   - bumpMinorPreMajor: true
     handleGHRelease: true
-    releaseType: java-lts
     branch: 7.0.x-lts
   - bumpMinorPreMajor: true
     handleGHRelease: true
-    releaseType: java-lts
     branch: 6.0.x-lts
-
-