tests: Trim .nim files trailing whitespace

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

tests/overload/toverl3.nim

@@ -4,8 +4,8 @@ discard """
 tup1'''
 """
 
-# Tests more specific generic match:
-
+# Tests more specific generic match:
+
 proc m[T](x: T) = echo "m2"
 proc m[T](x: var ref T) = echo "m1"
 
@@ -15,6 +15,6 @@ proc tup[S, T](x: tuple[a: S, b: T]) = echo "tup2"
 var
   obj: ref int
   tu: tuple[a: int, b: ref bool]
-  
+
 m(obj)
 tup(tu)