Note about using only forward slashes for PROFILE_DIR variable (conan-io#1333)

* note about using only forward slashes

* it is the path to directory, not to the file

* typo

Author: jgsogo

reference/profiles.rst

@@ -64,8 +64,9 @@ You can also show profile's content:
     [build_requires]
     [env]
 
-Use ``$PROFILE_DIR`` in your profile and it will be replaced with the absolute path to the profile file. It is useful to declare relative
-folders:
+Use ``$PROFILE_DIR`` in your profile and it will be replaced with the absolute path to
+the directory where the profile file is (this path will contain only forward slashes).
+It is useful to declare relative folders:
 
 .. code-block:: text