Remove support for # comments.

This CL removes support for parsing # style comments. Only the //
comments are accepted now.

Change-Id: I062c2a86149ecf828723c74f7168243678ee5870
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/38823
Commit-Queue: dan sinclair <dsinclair@chromium.org>
Commit-Queue: Ben Clayton <bclayton@google.com>
Auto-Submit: dan sinclair <dsinclair@chromium.org>
Reviewed-by: Ben Clayton <bclayton@google.com>

src/reader/wgsl/lexer.cc

@@ -143,8 +143,7 @@ void Lexer::skip_whitespace() {
 }
 
 void Lexer::skip_comments() {
-  // TODO(bclayton): Remove support for # comments
-  if (!matches(pos_, "#") && !matches(pos_, "//")) {
+  if (!matches(pos_, "//")) {
     return;
   }