path: use the correct name in validateString

The parameter was renamed from `ext` to `suffix`
but not in the `validateString` call.

Author: bpasero

lib/path.js

@@ -776,7 +776,7 @@ const win32 = {
    */
   basename(path, suffix) {
     if (suffix !== undefined)
-      validateString(suffix, 'ext');
+      validateString(suffix, 'suffix');
     validateString(path, 'path');
     let start = 0;
     let end = -1;
@@ -1336,7 +1336,7 @@ const posix = {
    */
   basename(path, suffix) {
     if (suffix !== undefined)
-      validateString(suffix, 'ext');
+      validateString(suffix, 'suffix');
     validateString(path, 'path');
 
     let start = 0;