tests: Trim .nim files trailing whitespace

via OSX: find . -name '*.nim' -exec sed -i '' -E 's/[[:space:]]+$//' {} +

tests/varres/tvarres3.nim

@@ -5,10 +5,10 @@ discard """
 var
   g = 5
 
-proc p(): var int = 
+proc p(): var int =
   var bla = addr(g) #: array [0..7, int]
   result = bla[]
-  
+
 p() = 45
 
 echo g