docs: reformat help page in usage docs (#788)

Signed-off-by: Jan Kowalleck <[email protected]>

docs/usage.rst

@@ -66,9 +66,9 @@ The full documentation can be issued by running with ``environment --help``:
 
     options:
       -h, --help            show this help message and exit
-     --PEP-639              Enable license gathering according to PEP 639 (improving license clarity with better package metadata).
+      --PEP-639             Enable license gathering according to PEP 639 (improving license clarity with better package metadata).
                             The behavior may change during the draft development of the PEP.
-     --gather-license-texts
+      --gather-license-texts
                             Enable license text gathering.
       --pyproject <file>    Path to the root component's `pyproject.toml` file.
                             This should point to a file compliant with PEP 621 (storing project metadata).