[wasm][debugger] Fix firefox tests (#71272)

* Fix firefox tests

* Update src/mono/wasm/debugger/BrowserDebugProxy/Firefox/FirefoxMonoProxy.cs
Co-authored-by: NAnkit Jain <radical@gmail.com>

* Remove whitespace
Co-authored-by: NAnkit Jain <radical@gmail.com>

src/mono/wasm/debugger/BrowserDebugProxy/Firefox/FirefoxMonoProxy.cs

@@ -1003,4 +1003,6 @@ internal override async Task<bool> OnGetScriptSource(MessageId msg_id, string sc
         return true;
     }
 
+    internal override Task<DebugStore> LoadStore(SessionId sessionId, bool tryUseDebuggerProtocol, CancellationToken token)
+        => base.LoadStore(sessionId, false, token);
 }

src/mono/wasm/debugger/BrowserDebugProxy/MonoProxy.cs

@@ -1469,7 +1469,7 @@ internal virtual async Task OnSourceFileAdded(SessionId sessionId, SourceFile so
             }
         }
 
-        internal async Task<DebugStore> LoadStore(SessionId sessionId, bool tryUseDebuggerProtocol, CancellationToken token)
+        internal virtual async Task<DebugStore> LoadStore(SessionId sessionId, bool tryUseDebuggerProtocol, CancellationToken token)
         {
             ExecutionContext context = GetContext(sessionId);