fix(pacmak): preserve correct prerelease label in Ruby gemspec version

Author: omarqureshi

packages/jsii-pacmak/lib/targets/version-utils.ts

@@ -263,7 +263,7 @@ export function toReleaseVersion(
           ? `post.${version.prerelease[rubyPostIdx + 1] ?? 0}`
           : undefined,
         rubyDevIdx > -1
-          ? `dev.${version.prerelease[rubyDevIdx + 1] ?? 0}`
+          ? `${version.prerelease[rubyDevIdx]}.${version.prerelease[rubyDevIdx + 1] ?? 0}`
           : undefined,
       ]
         .filter((v) => v)