ci: remove unnecessary env var, document signing plugin gotcha

Author: tronghn

.github/workflows/publish-release.yml

@@ -29,8 +29,8 @@ jobs:
         env:
           ORG_GRADLE_PROJECT_mavenCentralUsername: ${{ secrets.SONATYPE_USERNAME }}
           ORG_GRADLE_PROJECT_mavenCentralPassword: ${{ secrets.SONATYPE_PASSWORD }}
-          ORG_GRADLE_PROJECT_signingInMemoryKeyId: ${{ secrets.GPG_KEY_ID }}
           ORG_GRADLE_PROJECT_signingInMemoryKeyPassword: ${{ secrets.GPG_PASSPHRASE }}
+          # must be an armored (i.e. ascii) keypair with the private key _first_, followed by the public key
           ORG_GRADLE_PROJECT_signingInMemoryKey: ${{ secrets.GPG_KEYS }}
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         # The GITHUB_REF tag comes in the format 'refs/tags/xxx'.