Drop unused variables and lambda captures

Also, add context to connect() expressions where we are or were
capturing "this".

Change-Id: I6e006ba6f83d532478018550d148ee93eca59605
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>
Reviewed-by: hjk <hjk@qt.io>

src/plugins/coreplugin/jsexpander.cpp

@@ -84,7 +84,7 @@ JsExpander::JsExpander()
         QCoreApplication::translate("Core::JsExpander",
                                     "Evaluate simple JavaScript statements.<br>"
                                     "The statements may not contain '{' nor '}' characters."),
-        [this](QString in) -> QString {
+        [](QString in) -> QString {
             QString errorMessage;
             QString result = JsExpander::evaluate(in, &errorMessage);
             if (!errorMessage.isEmpty()) {