Fix Qt6 compat. (obsolete Qt regexp classes)

Author: PierreRaybaut

plotpy/widgets/colormap/manager.py

@@ -61,7 +61,8 @@ def __init__(self, parent: QW.QWidget | None = None, name: str = "") -> None:
 
         label = QW.QLabel(_("Enter a colormap name:"))
         self._edit = QW.QLineEdit()
-        self._edit.setValidator(QG.QRegExpValidator(QC.QRegExp("[1-9a-zA-Z_]*")))
+        regexp = QC.QRegularExpression("[1-9a-zA-Z_]*")
+        self._edit.setValidator(QG.QRegularExpressionValidator(regexp))
         self._edit.setText(name)
         self._edit.setToolTip(
             _(