runtime(erlang): add support for matchit plugin (#13713)

runtime(erlang): add support for matchit plugin (#13713)

This commit updates the Erlang runtime files to be in sync with the
`vim-erlang-runtime` repository. In particular, it adds the following
commit (with some cleanup and simplification afterwards):
https://github.com/vim-erlang/vim-erlang-runtime/commit/6ea8b85bc9c93b94c68ec53489a74f5687d898b0

Signed-off-by: Csaba Hoch <csaba.hoch@gmail.com>
Signed-off-by: Doug Kearns <dougkearns@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>