Bug 1668219 - [devtools] Remove unused devtools/client/shared/demangle.js. r=bomsy.

It was only used in the old perf panel.

Differential Revision: https://phabricator.services.mozilla.com/D145534

devtools/client/shared/moz.build

@@ -26,7 +26,6 @@ DevToolsModules(
     "autocomplete-popup.js",
     "css-angle.js",
     "curl.js",
-    "demangle.js",
     "devices.js",
     "enum.js",
     "events.js",

tools/rewriting/ThirdPartyPaths.txt

@@ -7,7 +7,6 @@ browser/extensions/formautofill/test/fixtures/third_party/
 browser/extensions/screenshots/build/raven.js
 devtools/client/inspector/markup/test/lib_*
 devtools/client/jsonview/lib/require.js
-devtools/client/shared/demangle.js
 devtools/client/shared/build/babel.js
 devtools/client/shared/source-map/
 devtools/client/shared/sourceeditor/codemirror/