Don't access static functions/fields via instance

Courtesy of readability-static-accessed-through-instance

Amends: b2a766a79a

Round #2: This time done with Qt Creator's Analyzer, which
found other occurences than run-clang-tidy.py

Change-Id: I479e280c7abcf2d24baccbb0af69ae4bda05198e
Reviewed-by: Jarek Kobus <jaroslaw.kobus@qt.io>

src/libs/clangsupport/connectionclient.cpp

@@ -288,7 +288,7 @@ bool ConnectionClient::waitForConnected()
             return isConnected;
         else {
             QThread::msleep(30);
-            QCoreApplication::instance()->processEvents();
+            QCoreApplication::processEvents();
         }
     }