build: lower minimum required version for webrtc-audio-processing to 0.3

This allows us to build with webrtc-audio-processing distro packages
currently available across supported Debian releases.

Change-Id: I25584a0564ceb78e8eefec78e5e903356c37ddab

configure.ac

@@ -558,7 +558,7 @@ if test "${SYS}" = "linux"; then
     [], [with_webrtc_ap=yes])
 
   AS_IF([test "x$with_webrtc_ap" = "xyes"],
-    [PKG_CHECK_MODULES(WEBRTC, [webrtc-audio-processing >= 0.3.1],
+    [PKG_CHECK_MODULES(WEBRTC, [webrtc-audio-processing >= 0.3],
       [AC_DEFINE([HAVE_WEBRTC_AP], 1,
          [Define if you have webrtc-audio-processing])],
       [AC_MSG_WARN([Missing webrtc-audio-processing development files])])])