change to use pr number

Author: Microsheep

doc/whats_new/v0.5.rst

@@ -21,7 +21,7 @@ Enhancement
 ...........
 
 - Add Parallelisation for SMOTEENN and SMOTETomek.
-  :issue:`541` by :user:`Michael Hsieh <Microsheep>`.
+  :issue:`547` by :user:`Michael Hsieh <Microsheep>`.
 
 Maintenance
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