Remove stdbool.h from files which don't need it

Done by manual inspection of the output of this script:
grep -r -l -w "bool\|true\|false" * | grep 'c$\|h$' > has_bool
grep -r -l "stdbool.h" * | grep 'c$\|h$' > has_include
grep -F -x -v -f has_bool has_include

src/nvim/api/buffer.h

@@ -2,7 +2,6 @@
 #define NVIM_API_BUFFER_H
 
 #include <stdint.h>
-#include <stdbool.h>
 
 #include "nvim/api/private/defs.h"
 

src/nvim/api/tabpage.h

@@ -2,7 +2,6 @@
 #define NVIM_API_TABPAGE_H
 
 #include <stdint.h>
-#include <stdbool.h>
 
 #include "nvim/api/private/defs.h"
 

src/nvim/api/vim.h

@@ -2,7 +2,6 @@
 #define NVIM_API_VIM_H
 
 #include <stdint.h>
-#include <stdbool.h>
 
 #include "nvim/api/private/defs.h"
 

src/nvim/api/window.h

@@ -2,7 +2,6 @@
 #define NVIM_API_WINDOW_H
 
 #include <stdint.h>
-#include <stdbool.h>
 
 #include "nvim/api/private/defs.h"
 

src/nvim/hashtab.h

@@ -1,7 +1,6 @@
 #ifndef NVIM_HASHTAB_H
 #define NVIM_HASHTAB_H
 
-#include <stdbool.h>
 #include "nvim/vim.h"
 
 /// Type for hash number (hash calculation result).

src/nvim/lib/klist.h

@@ -26,7 +26,6 @@
 #ifndef _AC_KLIST_H
 #define _AC_KLIST_H
 
-#include <stdbool.h>
 #include <stdlib.h>
 
 #include "nvim/memory.h"

src/nvim/os/msgpack_rpc.h

@@ -2,7 +2,6 @@
 #define NVIM_OS_MSGPACK_RPC_H
 
 #include <stdint.h>
-#include <stdbool.h>
 
 #include <msgpack.h>
 

src/nvim/os/server.c

@@ -1,7 +1,6 @@
 #include <stdlib.h>
 #include <string.h>
 #include <stdint.h>
-#include <stdbool.h>
 
 #include <uv.h>
 

src/nvim/os/shell.h

@@ -1,7 +1,6 @@
 #ifndef NVIM_OS_SHELL_H
 #define NVIM_OS_SHELL_H
 
-#include <stdbool.h>
 #include "nvim/types.h"
 
 // Flags for mch_call_shell() second argument