Drop redundant array initialization from ASSIGN_DIM tests

Author: jorgsowa

ext/opcache/tests/jit/assign_dim_019.phpt

@@ -20,7 +20,6 @@ set_error_handler(function ($errno, $errstr) {
 });
 
 function test() {
-    $a = [];
     $a[1.5] = new D;
 }
 

ext/opcache/tests/jit/assign_dim_020.phpt

@@ -20,7 +20,6 @@ set_error_handler(function ($errno, $errstr) {
 });
 
 function test() {
-    $a = [];
     $a[STDIN] = new D;
 }