tests: Trim .nim files trailing whitespace

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

tests/effects/teffects4.nim

@@ -8,12 +8,12 @@ type
   TObjB = object of TObj
     a, b, c: string
     fn: proc (): int {.tags: [FReadIO].}
-  
+
   EIO2 = ref object of EIO
 
 proc q() {.tags: [FIO].} =
   nil
-  
+
 proc raiser(): int =
   writeLine stdout, "arg"
   if true: