Revert "Add initial support for callable syntax"

This reverts commit d33f710.

Author: thekid

composer.json

@@ -7,7 +7,7 @@
   "keywords": ["module", "xp"],
   "require" : {
     "xp-framework/core": "^10.0 | ^9.0 | ^8.0 | ^7.0",
-    "xp-framework/ast": "dev-feature/first_class_callable_syntax as 7.4.0",
+    "xp-framework/ast": "^7.3",
     "php" : ">=7.0.0"
   },
   "require-dev" : {

src/main/php/lang/ast/emit/PHP.class.php

@@ -988,13 +988,6 @@ protected function emitNewClass($result, $new) {
     array_shift($result->type);
   }
 
-  protected function emitCallable($result, $callable) {
-    $t= $result->temp();
-    $result->out->write('fn(...'.$t.') => ');
-    $this->emitOne($result, $callable->expression);
-    $result->out->write('(... '.$t.')');
-  }
-
   protected function emitInvoke($result, $invoke) {
     $this->emitOne($result, $invoke->expression);
     $result->out->write('(');