JSON Wizards: Give labels more space even when word-wrapped

QLabel has a horizontal size policy of "Preferred", but if the label is
word-wrapped, the sizeHint is a using a golden ratio for width & height,
but we want the label to grab as much horizontal space as it gets
anyhow.

Change-Id: I6ed049f4f23158014dc04f2d5020b7c2dd4c1980
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/projectexplorer/jsonwizard/jsonfieldpage.cpp

@@ -388,6 +388,7 @@ QWidget *LabelField::createWidget(const QString &displayName, JsonFieldPage *pag
     auto w = new QLabel;
     w->setWordWrap(m_wordWrap);
     w->setText(m_text);
+    w->setSizePolicy(QSizePolicy::Expanding, w->sizePolicy().verticalPolicy());
     return w;
 }