lsp/protocol: make sure RenameProvider is an interface{}
lsp/protocol: make sure RenameProvider is an interface{}

CL 208272 made one occurrence of RenameProvider an interface{}.
This CL reflects the effect of making that change in the code
generator. (That is, the other occurrence of RenameProvider is now
an interface{} too.) gopls seems to still work, and all tests pass.

Change-Id: Icfc4a5639192c46b564509a601b8c03bbe2665a2
Reviewed-on: https://go-review.googlesource.com/c/tools/+/209158
Reviewed-by: Rebecca Stambler <d7cf11e5f299d88ea8348366a9fc4f7c335c3afa@golang.org>
Run-TryBot: Rebecca Stambler <d7cf11e5f299d88ea8348366a9fc4f7c335c3afa@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>

golang/tools,golang/tools,golang/tools,golang/tools,golang/tools