tests: Trim .nim files trailing whitespace

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

tests/stdlib/twalker.nim

@@ -1,13 +1,13 @@
-# iterate over all files with a given filter:
-
-import
-  "../../lib/pure/os.nim", ../../ lib / pure / times
-
-proc main(filter: string) =
-  for filename in walkFiles(filter):
-    writeLine(stdout, filename)
-
-  for key, val in envPairs():
-    writeLine(stdout, key & '=' & val)
-
-main("*.nim")
+# iterate over all files with a given filter:
+
+import
+  "../../lib/pure/os.nim", ../../ lib / pure / times
+
+proc main(filter: string) =
+  for filename in walkFiles(filter):
+    writeLine(stdout, filename)
+
+  for key, val in envPairs():
+    writeLine(stdout, key & '=' & val)
+
+main("*.nim")