[libcxx] [test] Fix comment typos, strip trailing whitespace.

No functional change, no code review.

llvm-svn: 292434
diff --git a/libcxx/test/std/experimental/filesystem/class.path/synop.pass.cpp b/libcxx/test/std/experimental/filesystem/class.path/synop.pass.cpp
index b0a7b5c..883feb2 100644
--- a/libcxx/test/std/experimental/filesystem/class.path/synop.pass.cpp
+++ b/libcxx/test/std/experimental/filesystem/class.path/synop.pass.cpp
@@ -32,7 +32,7 @@
   {
     ASSERT_SAME_TYPE(const path::value_type, decltype(path::preferred_separator));
     static_assert(path::preferred_separator == '/', "");
-    // Make preferred_separator ODR used by taking it's address.
+    // Make preferred_separator ODR used by taking its address.
     const char* dummy = &path::preferred_separator;
     ((void)dummy);
   }