Info.plist: drop dangling NSPrincipalClass=RApplication

Commit 23a9456 deleted the @interface RApplication : NSApplication
from ui/drivers/ui_cocoa.m when unifying the Cocoa + Metal event
pump on RAWindow : NSWindow.  The macOS Info.plist was left pointing
NSPrincipalClass at a class that no longer exists on the macOS side
(the iOS ui_cocoatouch.m RApplication is a separate UIApplication
subclass with its own Info.plist).

Harmless at runtime - AppKit's NSClassFromString lookup returns nil
and NSApplicationMain silently falls back to NSApplication, which
is what we want anyway - but a misleading breadcrumb.  Align with
the sibling pkg/apple/OSX/Info_Metal.plist and Info_AppStore.plist,
which already say NSApplication.

Affects the three xcodeprojs that consume OSX/Info.plist
(RetroArch.xcodeproj, RetroArch_OSX107.xcodeproj, RetroArch_PPC.
xcodeproj).  No behavioral change - they were already silently
using NSApplication before this cleanup.

Author: LibretroAdmin

pkg/apple/OSX/Info.plist

@@ -44,6 +44,6 @@
 	<key>NSHumanReadableCopyright</key>
 	<string>Copyright © 2025 RetroArch. All rights reserved.</string>
 	<key>NSPrincipalClass</key>
-	<string>RApplication</string>
+	<string>NSApplication</string>
 </dict>
 </plist>