Fix MSVC warning in MathCommon

https://bugs.webkit.org/show_bug.cgi?id=271835

Reviewed by Yusuke Suzuki.

In `toIntImpl` a warning, C4334, is emitted because MSVC is implicitly
converting the result of a 32-bit shift to 64-bit. By making an explicit
cast the warning is silenced.

* Source/JavaScriptCore/runtime/MathCommon.h:

Canonical link: https://commits.webkit.org/276799@main

Source/JavaScriptCore/runtime/MathCommon.h

@@ -158,13 +158,13 @@ ALWAYS_INLINE Int toIntImpl(double number)
             // As a result, the exp of the double is always >= 31. We can take advantage
             // of this by specifically checking for (exp == 31) and give the compiler a
             // chance to constant fold the operations below.
-            const constexpr UInt missingOne = 1U << intBitsMinusOne;
+            const constexpr UInt missingOne = static_cast<UInt>(1U) << intBitsMinusOne;
             result &= missingOne - 1;
             result += missingOne;
         }
     } else {
         if (exp < static_cast<int32_t>(intBits)) {
-            const UInt missingOne = 1U << exp;
+            const UInt missingOne = static_cast<UInt>(1U) << exp;
             result &= missingOne - 1;
             result += missingOne;
         }