Removed session pool mention from documentation comments

Author: ali-ince

src/v1/driver.js

@@ -175,15 +175,15 @@ class Driver {
   }
 
   /**
-   * Acquire a session to communicate with the database. The driver maintains
-   * a pool of sessions, so calling this method is normally cheap because you
-   * will be pulling a session out of the common pool.
+   * Acquire a session to communicate with the database. The session will
+   * borrow connections from the underlying connection pool as required and
+   * should be considered lightweight and disposable.
    *
    * This comes with some responsibility - make sure you always call
    * {@link close} when you are done using a session, and likewise,
    * make sure you don't close your session before you are done using it. Once
-   * it is returned to the pool, the session will be reset to a clean state and
-   * made available for others to use.
+   * it is closed, the underlying connection will be released to the connection
+   * pool and made available for others to use.
    *
    * @param {string} [mode=WRITE] the access mode of this session, allowed values are {@link READ} and {@link WRITE}.
    * @param {string|string[]} [bookmarkOrBookmarks=null] the initial reference or references to some previous