format: Update the maximum packetization time for iLBC 30.

In September 2006, the maximum packetization time (ptime) were set to such a
low value, packetization was disabled for many codecs actually. This was fixed
for many codecs but not for iLBC 30. This enables packetization for iLBC which
can be enabled for example via allow=ilbc:60,gsm,alaw,ulaw in the file sip.conf.

ASTERISK-7803

Change-Id: I2ef90023d35efb7cb8fe96ed74f53f6846ffad12