tests: Trim .nim files trailing whitespace

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

tests/controlflow/tnestif.nim

@@ -2,23 +2,23 @@ discard """
   file: "tnestif.nim"
   output: "i == 2"
 """
-# test nested ifs
-
-var
-    x, y: int
-x = 2
-if x == 0:
-    write(stdout, "i == 0")
-    if y == 0:
-        write(stdout, x)
-    else:
-        write(stdout, y)
-elif x == 1:
-    write(stdout, "i == 1")
-elif x == 2:
-    write(stdout, "i == 2")
-else:
-    write(stdout, "looks like Python")
-#OUT i == 2
+# test nested ifs
+
+var
+    x, y: int
+x = 2
+if x == 0:
+    write(stdout, "i == 0")
+    if y == 0:
+        write(stdout, x)
+    else:
+        write(stdout, y)
+elif x == 1:
+    write(stdout, "i == 1")
+elif x == 2:
+    write(stdout, "i == 2")
+else:
+    write(stdout, "looks like Python")
+#OUT i == 2