[GUI] Remove italics and use monospaced font for expression fields in…

… the attribute table. Related to issue #44638  (#59139)

* [gui] Remove italics and use monospaced font for expression fields in attribute tableThis commit modifies QgsFieldExpressionWidget to ensure that expression fields in the attribute table are displayed using a regular monospaced font instead of the default italics. This improves readability and ensures consistency between different parts of the interface.- Updated QgsFieldExpressionWidget::updateLineEditStyle() to set font to non-italic and apply monospaced family.- Addressed issue reported in #44638 regarding the readability challenges caused by italicized font in expression fields.Related issue: #44638

* [gui] Reformat code to match standard style

src/gui/qgsfieldexpressionwidget.cpp

@@ -392,7 +392,8 @@ void QgsFieldExpressionWidget::updateLineEditStyle( const QString &expression )
       currentField( &isExpression, &isValid );
     }
     QFont font = mCombo->lineEdit()->font();
-    font.setItalic( isExpression );
+    font.setFamily( ( QgsCodeEditor::getMonospaceFont() ).family() );
+    font.setItalic( false );
     mCombo->lineEdit()->setFont( font );
 
     if ( isExpression && !isValid )