Use correct github authentication.

src/main/resources/application-jenkins.properties

@@ -1,7 +1,7 @@
-git.username=${GIT_USERNAME}
+git.username=${GITHUB_USR}
 git.author=Spring Builds
 git.email=builds@springframework.org
-git.password=${GIT_PASSWORD}
+git.password=${GITHUB_TOKEN}
 
 git.gpg.keyname=6743E1BD
 git.gpg.passphrase=${GIT_SIGNING_KEY_PASSWORD}