[DevTools] CheckProtocolCompatibility.py -> check_protocol_compatibility.py

The CamelCase file is deprecated and I'd like to remove it at some point.

Change-Id: Iba491b01e5993ce2778c2ec58123e3aecafaf0ae
Reviewed-on: https://chromium-review.googlesource.com/c/1338346Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Commit-Queue: Johannes Henkel <johannes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57585}

src/inspector/BUILD.gn

@@ -30,7 +30,7 @@ _protocol_generated = [
 
 action("protocol_compatibility") {
   visibility = [ ":*" ]  # Only targets in this file can depend on this.
-  script = "$_inspector_protocol/CheckProtocolCompatibility.py"
+  script = "$_inspector_protocol/check_protocol_compatibility.py"
   inputs = [
     "js_protocol.pdl",
   ]