[CI] fix RAM counting with 5ms rendering

RAM numbers are not reported in the automatic complexity report since August 17th, see e.g. https://ivas-codec-pc.3gpp.org/ivas-codec/complexity-sba-hoa3-in-hoa3-out-public/index.html.

The reason seems to be that a call to update_mem() is missing in the first sub-frame for 5ms rendering/decoding in the decoder.