Avoid accessing global font settings from syntax highlighters

Change-Id: Ic015f7449351166ec41a7745355ddc63504f6442
Reviewed-by: André Hartmann <aha_1980@gmx.de>
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/vcsbase/baseannotationhighlighter.cpp

@@ -64,7 +64,7 @@ public:
 
 void BaseAnnotationHighlighterPrivate::updateOtherFormats()
 {
-    m_background = TextEditor::TextEditorSettings::fontSettings()
+    m_background = q->fontSettings()
                        .toTextCharFormat(TextEditor::C_TEXT)
                        .brushProperty(QTextFormat::BackgroundBrush)
                        .color();