fix: documentation for --allow-extra-fields (#2416)

* fix documentation for --allow-extra-fields

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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---------

Co-authored-by: Cosmo Grant <cosmo.grant@postcodelottery.co.uk>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: 3 people

README.md

@@ -439,9 +439,8 @@ Field customization:
                         Use schema description to populate field docstring
 
 Model customization:
-  --allow-extra-fields  Deprecated: Allow passing extra fields, if this flag is not passed,
-                        extra fields are forbidden. This flag is deprecated. Use `--extra-
-                        fields=allow` instead.
+  --allow-extra-fields  Deprecated: Allow passing extra fields. This flag is deprecated. Use
+                        `--extra-fields=allow` instead.
   --allow-population-by-field-name
                         Allow population by field name
   --class-name CLASS_NAME

docs/index.md

@@ -431,9 +431,8 @@ Field customization:
                         Use schema description to populate field docstring
 
 Model customization:
-  --allow-extra-fields  Deprecated: Allow passing extra fields, if this flag is not passed,
-                        extra fields are forbidden. This flag is deprecated. Use `--extra-
-                        fields=allow` instead.
+  --allow-extra-fields  Deprecated: Allow passing extra fields. This flag is deprecated. Use
+                        `--extra-fields=allow` instead.
   --allow-population-by-field-name
                         Allow population by field name
   --class-name CLASS_NAME

src/datamodel_code_generator/arguments.py

@@ -97,8 +97,7 @@ def start_section(self, heading: str | None) -> None:
 # ======================================================================================
 extra_fields_model_options.add_argument(
     "--allow-extra-fields",
-    help="Deprecated: Allow passing extra fields, if this flag is not passed, extra fields are forbidden. "
-    "This flag is deprecated. Use `--extra-fields=allow` instead.",
+    help="Deprecated: Allow passing extra fields. This flag is deprecated. Use `--extra-fields=allow` instead.",
     action="store_true",
     default=None,
 )