gdb: remove some unnecessary frame_info_ptr resets

This code was probably needed before we had reinflatable
frame_info_ptrs, it's not necessary anymore.

Change-Id: I5474c6081ee1e39624c9266b05dbe01351a130b5
Approved-By: Tom Tromey <tom@tromey.com>

gdb/infrun.c

@@ -8848,9 +8848,6 @@ insert_exception_resume_breakpoint (struct thread_info *tp,
 					       handler,
 					       bp_exception_resume).release ();
 
-	  /* set_momentary_breakpoint_at_pc invalidates FRAME.  */
-	  frame = nullptr;
-
 	  tp->control.exception_resume_breakpoint = bp;
 	}
     }