Remove a couple of unnecessary temporary variables in MurmurHash3_64.hexdigest

These variables are left-over from the initial implementation, back when `String.prototype.padStart` didn't exist and we thus had to pad manually (using a loop).

src/shared/murmurhash3.js

@@ -130,9 +130,10 @@ class MurmurHash3_64 {
       (((((h2 << 16) | (h1 >>> 16)) * 0xb9fe1a85) & MASK_HIGH) >>> 16);
     h1 ^= h2 >>> 1;
 
-    const hex1 = (h1 >>> 0).toString(16),
-      hex2 = (h2 >>> 0).toString(16);
-    return hex1.padStart(8, "0") + hex2.padStart(8, "0");
+    return (
+      (h1 >>> 0).toString(16).padStart(8, "0") +
+      (h2 >>> 0).toString(16).padStart(8, "0")
+    );
   }
 }