[processing] Disable cancel button for GDAL algorithms

The provider doesn't support cancelation

(cherry-picked from d164f8f)

Author: nyalldawson

python/plugins/processing/algs/gdal/GdalAlgorithm.py

@@ -59,6 +59,9 @@ def createInstance(self, config={}):
     def createCustomParametersWidget(self, parent):
         return GdalAlgorithmDialog(self)
 
+    def flags(self):
+        return QgsProcessingAlgorithm.FlagSupportsBatch # cannot cancel!
+
     def getConsoleCommands(self, parameters, context, feedback, executing=True):
         return None