fix string whivch should have been an f-string (#21192)

Needs to be an f-string in order for the replacement to occur ...

src/python/pants/core/util_rules/environments.py

@@ -197,7 +197,7 @@ class LocalWorkspaceEnvironmentTarget(Target):
         LocalWorkspaceCompatiblePlatformsField,
     )
     help = help_text(
-        """
+        f"""
         Configuration of a "workspace" execution environment for specific platforms.
 
         A "workspace" environment is a local environment which executes build processes within