hgweb: fix error in docstring
Despite the subtle semantic difference, this sentence really meant to
say "overridden", not "overwritten".
#require rustfmt test-repo
$ . "$TESTDIR/helpers-testrepo.sh"
$ cd "$TESTDIR"/..
$ RUSTFMT=$(rustup which --toolchain nightly rustfmt)
$ for f in `testrepohg files 'glob:**/*.rs'` ; do
> $RUSTFMT --check --unstable-features --color=never $f
> done