sidplayfp: Ignore tags with letters in them

I don't want to keep adding suffixes to this exclusion rule... Just ignore anything that has a letter in it.

Leading `v` is stripped before the check, so this should work fine.

pkgs/by-name/si/sidplayfp/package.nix

@@ -72,7 +72,7 @@ stdenv.mkDerivation (finalAttrs: {
     };
     updateScript = gitUpdater {
       rev-prefix = "v";
-      ignoredVersions = "(a|rc)";
+      ignoredVersions = "[a-zA-Z]";
     };
   };