remove unnecessary file Pal/include/pal/.gdb_history.

The file, Pal/include/pal/.gdb_history, seems committed accidentally.
So remove it.

Pal/include/pal/.gdb_history

@@ -1,58 +0,0 @@
-b create_slab_mgr 
-r
-n
-p mem
-fin
-p $2
-p *$2
-q
-b main
-r
-n
-p mgr
-n
-n
-p mgr
-p *mgr
-q
-r
-q
-r
-q
-b 21
-r
-p *mgr
-q
-r
-bt
-p prev
-up
-p head
-p head->prev
-p new
-p head
-down
-list
-p next
-p prev
-up
-p head->prev
-p *head->prev
-up
-up
-q
-r
-up
-up
-up
-down
-list
-p i
-p obj
-p *obj
-q
-r
-q
-r
-p area
-q