Merge bitcoin-core/gui#579: Getting ready to Qt 6 (2/n). Remove QApplication::globalStrut()

3eaf5dbfe0 qt: Remove `QApplication::globalStrut()` call (Hennadii Stepanov)

Pull request description:

  This function has been deprecated in Qt 5.15.0, and has been [removed](https://github.com/qt/qtbase/commit/033d01bd6e2aef740ad1408a04d3ca0ae3b9ba9b) in Qt 6.

ACKs for top commit:
  jarolrod:
    ACK 3eaf5dbfe0
  luke-jr:
    utACK 3eaf5dbfe0

Tree-SHA512: 71ee539b6ffa3755f7e6beaa72a8937886471e298830878def6dd9f48c601611d94d52c638bc1602f938df2ba84ff8b130ea8da8e6c08ae7146173fa613a5003

src/qt/bitcoinamountfield.cpp

@@ -144,8 +144,7 @@ public:
 
             opt.rect = rect();
 
-            cachedMinimumSizeHint = style()->sizeFromContents(QStyle::CT_SpinBox, &opt, hint, this)
-                                    .expandedTo(QApplication::globalStrut());
+            cachedMinimumSizeHint = style()->sizeFromContents(QStyle::CT_SpinBox, &opt, hint, this);
         }
         return cachedMinimumSizeHint;
     }