Fix clang-tidy redundant return/continue warnings

Author: nyalldawson

src/app/qgisapp.cpp

@@ -5550,7 +5550,6 @@ void QgisApp::openProject( const QString &fileName )
     // error handling and reporting is in addProject() function
     addProject( fileName );
   }
-  return;
 }
 
 /**
@@ -11823,7 +11822,6 @@ void QgisApp::oldProjectVersionWarning( const QString &oldVersion )
 
     messageBar()->pushMessage( title, smalltext );
   }
-  return;
 }
 
 void QgisApp::updateUndoActions()

src/app/qgscustomprojectiondialog.cpp

@@ -365,7 +365,6 @@ void QgsCustomProjectionDialog::on_leNameList_currentItemChanged( QTreeWidgetIte
     teParameters->setPlainText( QLatin1String( "" ) );
     return;
   }
-  return;
 }
 
 void QgsCustomProjectionDialog::on_pbnCopyCRS_clicked()

src/core/geometry/qgsgeos.cpp

@@ -300,8 +300,6 @@ void QgsGeos::subdivideRecursive( const GEOSGeometry *currentPart, int maxNodes,
   {
     subdivideRecursive( clipPart2.get(), maxNodes, depth, parts, halfClipRect2 );
   }
-
-  return;
 }
 
 QgsAbstractGeometry *QgsGeos::subdivide( int maxNodes, QString *errorMsg ) const

src/core/geometry/qgstriangle.cpp

@@ -241,7 +241,6 @@ QgsAbstractGeometry *QgsTriangle::toCurveType() const
 void QgsTriangle::addInteriorRing( QgsCurve *ring )
 {
   Q_UNUSED( ring );
-  return;
 }
 
 bool QgsTriangle::deleteVertex( QgsVertexId position )

src/core/processing/models/qgsprocessingmodelalgorithm.cpp

@@ -488,8 +488,6 @@ QMap<QString, QgsProcessingModelAlgorithm::VariableDefinition> QgsProcessingMode
     variables.insert( safeName( QStringLiteral( "%1_miny" ).arg( name ) ), VariableDefinition( layer ? layer->extent().yMinimum() : QVariant(), source, QObject::tr( "Minimum Y of %1" ).arg( description ) ) );
     variables.insert( safeName( QStringLiteral( "%1_maxx" ).arg( name ) ), VariableDefinition( layer ? layer->extent().xMaximum() : QVariant(), source, QObject::tr( "Maximum X of %1" ).arg( description ) ) );
     variables.insert( safeName( QStringLiteral( "%1_maxy" ).arg( name ) ), VariableDefinition( layer ? layer->extent().yMaximum() : QVariant(), source, QObject::tr( "Maximum Y of %1" ).arg( description ) ) );
-
-    continue;
   }
 
   sources = availableSourcesForChild( childId, QStringList()