Bump RLS to latest master on rust-lang/rls

Of primary interest, this merges
rust-lang/rls@ece09b8 into rust-lang/rust,
which brings in the changes that fix RLS tests broken by rust-lang#97853. rust-lang#97853 already
introduced that commit's changes (under
27f4044df03d15c7c38a483c3e4635cf4f51807d) but without putting those changes on
rust-lang/rls as a branch, so we ended up with an orphan commit that caused
trouble when updating submodules in rust-lang/rust.

This commit, once merged into rust-lang/rust, should continue to let RLS tests
to pass on rust-lang/rust's side and move us back into a healthy state where tip
of the submodule points to a valid master commit in the rust-lang/rls
repository.

Cargo.lock

@@ -3101,7 +3101,6 @@ name = "racer"
 version = "2.2.2"
 dependencies = [
  "bitflags",
- "clap 2.34.0",
  "derive_more",
  "env_logger 0.7.1",
  "humantime 2.0.1",
@@ -3325,7 +3324,7 @@ dependencies = [
  "difference",
  "env_logger 0.9.0",
  "futures 0.3.19",
- "heck 0.3.1",
+ "heck 0.4.0",
  "home",
  "itertools",
  "jsonrpc-core",