check_spelling: correct help text formatting, correct "--check" text

tools/check_source/check_spelling.py

@@ -712,9 +712,10 @@ def spell_check_file_with_cache_support(
 
 def argparse_create() -> argparse.ArgumentParser:
 
-    # When --help or no args are given, print this help
-    description = __doc__
-    parser = argparse.ArgumentParser(description=description)
+    parser = argparse.ArgumentParser(
+        description=__doc__,
+        formatter_class=argparse.RawTextHelpFormatter,
+    )
 
     parser.add_argument(
         "--match",
@@ -750,10 +751,10 @@ def argparse_create() -> argparse.ArgumentParser:
         required=False,
         metavar='CHECK_TYPE',
         help=(
-            'Text to extract for checking.\n'
+            'The check to perform.\n'
             '\n'
-            '- ``COMMENTS`` extracts comments from source code.\n'
-            '- ``STRINGS`` extracts text.'
+            '- ``SPELLING`` check spelling.\n'
+            '- ``DUPLICATES`` report repeated words.'
         ),
     )