[iOS] Remove implementation of RunOpenPanel from Brave's web client (#33565)

These methods are implemented by a Chrome tab helper that isn't bridged to CWVWebView, so for now we can remove it. This fixes a crash if a user happened to enable the `kIOSCustomFileUploadMenu` feature flag from `brave://flags` which is disabled by default.

ios/browser/web/brave_web_client.h

@@ -50,6 +50,14 @@ class BraveWebClient : public ChromeWebClient {
   bool ShouldBlockUniversalLinks(web::WebState* web_state,
                                  NSURLRequest* request) override;
 
+  bool CanRunOpenPanel(web::WebState* web_state) const override
+      API_AVAILABLE(ios(18.4));
+  void RunOpenPanel(web::WebState* web_state,
+                    WKOpenPanelParameters* parameters,
+                    WKFrameInfo* frame,
+                    base::OnceCallback<void(NSArray<NSURL*>*)> completion)
+      const override API_AVAILABLE(ios(18.4));
+
  private:
   std::string legacy_user_agent_;
 };

ios/browser/web/brave_web_client.mm

@@ -8,6 +8,7 @@
 #include "base/feature_list.h"
 #include "base/functional/bind.h"
 #include "base/ios/ns_error_util.h"
+#include "base/notimplemented.h"
 #include "base/strings/sys_string_conversions.h"
 #include "brave/components/constants/url_constants.h"
 #include "brave/ios/browser/api/web_view/brave_web_view_internal.h"
@@ -192,3 +193,17 @@ NSString* BraveWebClient::GetUserAgentForRequest(
   }
   return nil;
 }
+
+bool BraveWebClient::CanRunOpenPanel(web::WebState* source) const
+    API_AVAILABLE(ios(18.4)) {
+  return false;
+}
+
+void BraveWebClient::RunOpenPanel(
+    web::WebState* source,
+    WKOpenPanelParameters* parameters,
+    WKFrameInfo* frame,
+    base::OnceCallback<void(NSArray<NSURL*>*)> completion) const
+    API_AVAILABLE(ios(18.4)) {
+  NOTIMPLEMENTED();
+}