fix[react-devtools]: removed redundant startProfiling call (#31131)

Stacked on #31118. See last
commit.

We don't need to call `startProfiling()` here, because we delegate this
to the Renderer itself:

https://github.com/facebook/react/blob/830e823cd2c6ee675636d31320b10350e8ade9ae/packages/react-devtools-shared/src/backend/fiber/renderer.js#L5227-L5232

Since this is de-facto the constructor of Renderer, this will be called
earlier.

Validated via testing the reload-to-profile for Chrome browser
extension.

packages/react-devtools-shared/src/backend/agent.js

@@ -714,10 +714,6 @@ export default class Agent extends EventEmitter<{
   ) {
     this._rendererInterfaces[rendererID] = rendererInterface;
 
-    if (this._isProfiling) {
-      rendererInterface.startProfiling(this._recordChangeDescriptions);
-    }
-
     rendererInterface.setTraceUpdatesEnabled(this._traceUpdatesEnabled);
 
     // When the renderer is attached, we need to tell it whether