npm-update: Drop alpha versions for @patternfly

The "alpha" and "prerelease" tags are currently very inconsistent in the
various @patternfly projects, and even go backwards. Stay at the stable
releases for the time being.

npm-update

@@ -58,8 +58,6 @@ def write_package_json(package_json_path, data):
 def prefix(name, version):
     if not version[0].isdigit():
         return version
-    if name.startswith("@patternfly"):
-        return "alpha"
     return "~" + version