tests: Trim .nim files trailing whitespace

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

tests/modules/mrecmod2.nim

@@ -1,9 +1,9 @@
 # Module B
-import trecmod2  
+import trecmod2
 
 proc p*(x: trecmod2.T1): trecmod2.T1 =
   # this works because the compiler has already
   # added T1 to trecmod2's interface symbol table
   return x + 1
-  
+