Clarify references to legacy PHP driver

Author: jmikola

source/release-notes/3.0.txt

@@ -454,7 +454,7 @@ replica sets:
 - Ruby Driver 2.0
 - Node.JS Driver 2.0
 
-The C, C++, Perl, and PHP drivers, as well as the earlier versions of
+The C, C++, Perl, and legacy PHP drivers, as well as the earlier versions of
 the Ruby, Python, and Node.JS drivers, discover and monitor replica set
 members serially, and thus are not suitable for use with large replica
 sets.

source/release-notes/drivers-write-concern.txt

@@ -71,6 +71,6 @@ driver-specific changes.
 - Java, version 2.10.0
 - Node.js, version 1.2
 - Perl, version 0.501.1
-- PHP, version 1.4
+- Legacy PHP, version 1.4
 - Python, version 2.4
 - Ruby, version 1.8