QMessageAuthenticationCode: make reset() noexcept

This is the last method that can and should be noexcept:

- the ctor allocates the Private, so can't be
- static hash() allocates QByteArray::data(), so also cannot be
- ditto result()

All other functions are already noexcept.

Fixes: QTBUG-111688
Change-Id: I237c3d1292452da5ca92712531c3527c1fb2f59b
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

src/corelib/tools/qcryptographichash.cpp

@@ -1307,7 +1307,7 @@ QMessageAuthenticationCode::~QMessageAuthenticationCode()
 /*!
     Resets message data. Calling this method doesn't affect the key.
 */
-void QMessageAuthenticationCode::reset()
+void QMessageAuthenticationCode::reset() noexcept
 {
     d->result.clear();
     d->messageHash.reset();

src/corelib/tools/qmessageauthenticationcode.h

@@ -31,7 +31,7 @@ public:
     void swap(QMessageAuthenticationCode &other) noexcept
     { qt_ptr_swap(d, other.d); }
 
-    void reset();
+    void reset() noexcept;
 
 #if QT_CORE_REMOVED_SINCE(6, 6)
     void setKey(const QByteArray &key);