[processing] add tags to statistics by categories algorithm

Author: nirvn

python/plugins/processing/algs/qgis/StatisticsByCategories.py

@@ -58,6 +58,9 @@ def group(self):
     def groupId(self):
         return 'vectoranalysis'
 
+    def tags(self):
+        return self.tr('groups').split(',')
+
     def __init__(self):
         super().__init__()