Use first line comment prefix when toggling comments (#10335)

This fixed an issue introduced in
https://github.com/zed-industries/zed/pull/10126, where, when toggling
comments in a language with multiple line comment prefixes (e.g. Gleam,
Erlang) Zed would insert the *last* prefix instead of the first.

Release Notes:

- Fixed an issue where the `toggle comments` command inserted the wrong
line comment prefix in some languages (preview only).

Co-authored-by: Marshall <marshall@zed.dev>

crates/languages/src/rust/config.toml

@@ -1,7 +1,7 @@
 name = "Rust"
 grammar = "rust"
 path_suffixes = ["rs"]
-line_comments = [ "/// ", "//! ", "// "]
+line_comments = ["// ", "/// ", "//! "]
 autoclose_before = ";:.,=}])>"
 brackets = [
     { start = "{", end = "}", close = true, newline = true },