Fix Zstd compressor ID

Author: thekid

src/main/php/com/mongodb/io/Zstd.class.php

@@ -1,7 +1,7 @@
 <?php namespace com\mongodb\io;
 
 class Zstd extends Compressor {
-  public $id= 2;
+  public $id= 3;
   public $level;
 
   /** @param int $level */

src/test/php/com/mongodb/unittest/CompressionTest.class.php

@@ -72,6 +72,6 @@ public function negotiate_zlib_with($options, $level) {
 
   #[Test, Runtime(extensions: ['zstd'])]
   public function negotiate_zstd() {
-    Assert::instance(Zstd::class, Compression::negotiate(['unsupported', 'zstd'])->select(2));
+    Assert::instance(Zstd::class, Compression::negotiate(['unsupported', 'zstd'])->select(3));
   }
 }