do not require igbinary

Change-Id: I41114f9b9ed51194eea1deec61e7a39e2877bf36
Reviewed-on: http://review.couchbase.org/109530
Tested-by: Build Bot <[email protected]>
Reviewed-by: Sergey Avseyev <[email protected]>

Author: avsej

package.xml

@@ -152,16 +152,9 @@
                 <min>7.1.0</min>
             </php>
             <pearinstaller>
-                <min>1.10.7</min>
+                <min>1.10.1</min>
             </pearinstaller>
         </required>
-        <optional>
-            <package>
-                <name>igbinary</name>
-                <channel>pecl.php.net</channel>
-                <providesextension>igbinary</providesextension>
-            </package>
-        </optional>
     </dependencies>
     <providesextension>couchbase</providesextension>
     <extsrcrelease/>