Remove unused autotools macro AC_COMPILE_CHECK_SIZEOF

The AC_COMPILE_CHECK_SIZEOF is from the GNU Autoconf Archive and was
renamed to AX_COMPILE_CHECK_SIZEOF. However this macro is not used in
current MongoDB PHP extension nor in the mongo-c-driver dependency
anymore.

Author: petk

config.m4

@@ -246,7 +246,6 @@ if test "$PHP_MONGODB" != "no"; then
     ])
 
     dnl Avoid using AC_CONFIG_MACRO_DIR, which might conflict with PHP
-    _include([scripts/autotools/m4/ac_compile_check_sizeof.m4])
     _include([scripts/autotools/m4/as_var_copy.m4])
     _include([scripts/autotools/m4/ax_check_compile_flag.m4])
     _include([scripts/autotools/m4/ax_prototype.m4])