fix(cli): remove duplicate usage (#308)

Author: cclauss

README.md

@@ -22,7 +22,7 @@ Or to run __gyp-next__ directly without installing it:
 * `uvx --from=gyp-next gyp --help`
 ```
 NOTE: running app 'gyp' from 'gyp-next'
-usage: usage: gyp [options ...] [build_file ...]
+usage: gyp [options ...] [build_file ...]
 
 options:
   -h, --help            show this help message and exit

pylib/gyp/__init__.py

@@ -345,7 +345,7 @@ def parse_args(self, *args):
 
 def gyp_main(args):
     my_name = os.path.basename(sys.argv[0])
-    usage = "usage: %(prog)s [options ...] [build_file ...]"
+    usage = "%(prog)s [options ...] [build_file ...]"
 
     parser = RegeneratableOptionParser(usage=usage.replace("%s", "%(prog)s"))
     parser.add_argument(