tests: Trim .nim files trailing whitespace

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

tests/stckovfl.nim

@@ -1,10 +1,10 @@
 # To test stack overflow message
 
-proc over(a: int): int = 
+proc over(a: int): int =
   if a >= 10:
     assert false
     return
   result = over(a+1)+5
-  
+
 Echo($over(0))