Bug 1737255 - [devtools] Remove backward compatibilty code for this.traits r=jdescottes

Differential Revision: https://phabricator.services.mozilla.com/D129256

devtools/client/framework/test/browser_target_parents.js

@@ -22,7 +22,7 @@ add_task(async function() {
   await testGetTargetWithConcurrentCalls(tabDescriptors, tabTarget => {
     // We only call BrowsingContextTargetFront.attach and not TargetMixin.attachAndInitThread.
     // So very few things are done.
-    return !!tabTarget.traits;
+    return !!tabTarget.targetForm?.traits;
   });
 
   await client.close();

devtools/client/fronts/targets/target-mixin.js

@@ -272,12 +272,6 @@ function TargetMixin(parentClass) {
      * @return {Mixed}
      */
     getTrait(traitName) {
-      // @backward-compat { version 93 } All traits should be on the `targetForm`, remove
-      // this backward compatibility code.
-      if (this.traits && this.traits[traitName]) {
-        return this.traits[traitName];
-      }
-
       // If the targeted actor exposes traits and has a defined value for this
       // traits, override the root actor traits
       if (this.targetForm.traits && traitName in this.targetForm.traits) {

devtools/client/fronts/targets/window-global.js

@@ -121,10 +121,6 @@ class WindowGlobalTargetFront extends TargetMixin(
       const response = await super.attach();
 
       this.targetForm.threadActor = response.threadActor;
-
-      // @backward-compat { version 93 } Remove this. All the traits are on form and can be accessed
-      // using getTraits.
-      this.traits = response.traits || {};
     })();
     return this._attach;
   }