Fix unused param warnings

Summary:
Compiler: GCC 7.3.1
Distro: Arch Linux

Compiler warnings:

```
/home/vlad/KDE/src/kde/workspace/kwin/effects/blur/blur.cpp: In member function ‘void KWin::BlurEffect::upscaleRenderToScreen(KWin::GLVertexBuffer*, int, int, QMatrix4x4, QRect, QPoint)’:
/home/vlad/KDE/src/kde/workspace/kwin/effects/blur/blur.cpp:677:129: warning: unused parameter ‘windowShape’ [-Wunused-parameter]
 void BlurEffect::upscaleRenderToScreen(GLVertexBuffer *vbo, int vboStart, int blurRectCount, QMatrix4x4 screenProjection, QRect windowShape, QPoint windowPosition)
                                                                                                                                 ^~~~~~~~~~~
```

```
/home/vlad/KDE/src/kde/workspace/kwin/main_wayland.cpp: In function ‘void KWin::{anonymous}::gainRealTime(KWin::RealTimeFlags)’:
/home/vlad/KDE/src/kde/workspace/kwin/main_wayland.cpp:95:56: warning: unused parameter ‘flags’ [-Wunused-parameter]
 void gainRealTime(RealTimeFlags flags = RealTimeFlags::DontReset)
```

Reviewers: #kwin, davidedmundson

Reviewed By: davidedmundson

Subscribers: anemeth, kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D12208