Allow to git tag containing v as prefix (#1481)

We've decided to specify git tag versions with a `v` prefix for all
bot-sdk repositories. This is to apply the same rule across all
repositories and reduce mistakes.

In the case of line-bot-sdk-java, specifying the `v` prefix is not an
issue as long as it is removed during publishing. This change supports
it.

Author: Yang-33

.github/workflows/publish.yml

@@ -42,6 +42,7 @@ jobs:
           else
             VERSION=${{ github.event.release.tag_name }}
           fi
+          VERSION=${VERSION#v}
           echo "VERSION=$VERSION" >> $GITHUB_ENV
 
       - name: Publish package