commit: fix a wrong argument name in documentation

Differential Revision: https://phab.mercurial-scm.org/D8985

mercurial/commit.py

@@ -223,7 +223,7 b' def _filecommit('
         manifest2:  manifest of changeset second parent
         linkrev:    revision number of the changeset being created
         tr:         current transation
-        individual: boolean, set to False to skip storing the copy data
+        includecopymeta: boolean, set to False to skip storing the copy data
                     (only used by the Google specific feature of using
                     changeset extra as copy source of truth).