Port MR1825 from float - Bug in renderer flush in ISM JBM bitrate switching
# Basic Info <!--- Remember to add issue and MR links to the status page in wiki here https://forge.3gpp.org/rep/sa4/audio/ivas-basop/-/wikis/IVAS-PC-MR-conversion-status--> - Original merge request in float repo: ivas-codec-pc/ivas-codec!1825
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