Cleanup duplicated check

Author: remicollet

config.m4

@@ -235,7 +235,6 @@ if test "$PHP_MONGODB" != "no"; then
     PHP_EVAL_LIBLINE($PHP_MONGODB_BSON_LIBS, MONGODB_SHARED_LIBADD)
     AC_DEFINE(HAVE_SYSTEM_LIBBSON, 1, [Use system libbson])
 
-    AC_PATH_PROG(PKG_CONFIG, pkg-config, no)
     AC_MSG_CHECKING(for libmongoc)
     if test -x "$PKG_CONFIG" && $PKG_CONFIG --exists libmongoc-1.0; then
       if $PKG_CONFIG libmongoc-1.0 --atleast-version 1.16.1; then
@@ -254,7 +253,6 @@ if test "$PHP_MONGODB" != "no"; then
     AC_DEFINE(HAVE_SYSTEM_LIBMONGOC, 1, [Use system libmongoc])
 
     if test "$PHP_MONGODB_CLIENT_SIDE_ENCRYPTION" != "no"; then
-      AC_PATH_PROG(PKG_CONFIG, pkg-config, no)
       AC_MSG_CHECKING(for libmongocrypt)
 
       if test -x "$PKG_CONFIG" && $PKG_CONFIG --exists libmongocrypt; then