Fix release workflow (#390)

Author: trask

.github/scripts/update-version.sh

@@ -0,0 +1,7 @@
+#!/bin/bash -e
+
+version=$1
+
+sed -Ei "s/val snapshot = true/val snapshot = false/" build.gradle.kts
+
+sed -Ei "1 s/(Comparing source compatibility of [a-z-]+)-[0-9]+\.[0-9]+\.[0-9]+(-SNAPSHOT)?.jar/\1-$version.jar/" docs/apidiffs/current_vs_latest/*.txt

.github/workflows/prepare-release-branch.yml

@@ -52,7 +52,7 @@ jobs:
           echo "RELEASE_BRANCH_NAME=$release_branch_name" >> $GITHUB_ENV
 
       - name: Update version
-        run: sed -Ei "s/val snapshot = true/val snapshot = false/" build.gradle.kts
+        run: .github/scripts/update-version.sh $VERSION
 
       - name: Update the change log with the approximate release date
         run: |