tests: Trim .nim files trailing whitespace

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

tests/objects/tobjcov.nim

@@ -5,10 +5,10 @@ type
     a: int
   TB = object of TA
     b: array[0..5000_000, int]
-    
+
 proc ap(x: var TA) = x.a = -1
 proc bp(x: var TB) = x.b[high(x.b)] = -1
-    
+
 # in Nim proc (x: TB) is compatible to proc (x: TA),
 # but this is not type safe:
 var f = cast[proc (x: var TA) {.nimcall.}](bp)