Debugger: Simplify code

isReverseDebuggingEnabled() always returns true for GDB nowadays.

Change-Id: Ic5500a9b191dafc2e9893d75f584a6b304c43a8f
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/debugger/debuggerplugin.cpp

@@ -2021,14 +2021,6 @@ void addDebugInfoTask(unsigned id, const QString &cmd)
     dd->m_debugInfoTaskHandler.addTask(id, cmd);
 }
 
-bool isReverseDebuggingEnabled()
-{
-    return true;
-
-    static bool enabled = qEnvironmentVariableIsSet("QTC_DEBUGGER_ENABLE_REVERSE");
-    return enabled;
-}
-
 void DebuggerPluginPrivate::extensionsInitialized()
 {
     // If the CppEditor or QmlJS editor plugin is there, we want to add something to