Misc. typos

Found via ` codespell -q 3 -S *.ts,*.xml -L ba,froms,seeked`

effects/fields/combofield.h

@@ -85,7 +85,7 @@ private slots:
    *
    * The current index of the QWidget (QComboBox in this case). Automatically set when this slot is connected
    * to the QComboBox::currentIndexChanged() signal. This is the only time ComboFields deal with indices since the
-   * QComboBox's indices will match precisely to the items_ array. Outside of this function, QVariant data is prefered.
+   * QComboBox's indices will match precisely to the items_ array. Outside of this function, QVariant data is preferred.
    */
   void UpdateFromWidget(int index);
 };

effects/shaders/chromakey.frag

@@ -2,7 +2,7 @@
 (c) 2008 Edward Cannon (adapted to GLSL by Olive Team)
 feel free to use or modify at will*/
  
-/*the follwing three functions convert RGB into YCbCr in the same manner as in JPEG images*/ 
+/*the following three functions convert RGB into YCbCr in the same manner as in JPEG images*/ 
 
 uniform sampler2D tex;
 varying vec2 vTexCoord;