fix typo

(cherry picked from commit 658cfe68c91ec24f04f8ebda307fbec7d55a412f)

Author: jef-n

python/plugins/processing/algs/help/qgis.yaml

@@ -486,7 +486,7 @@ qgis:splitlineswithlines: >
 qgis:splitvectorlayer: >
   This algorithm takes a vector layer and an attribute and generates a set of vector layers in an output folder. Each of the layers created in that folder contains all features from the input layer with the same value for the specified attribute.
 
-  The number of files generated is equal to the nubmer of different values found for the specified attribute.
+  The number of files generated is equal to the number of different values found for the specified attribute.
 
 qgis:statisticsbycategories: