Remove the block of $KAFKA_HEAP_OPTS from start-kafka.sh

[thangola]

if [[ -n "$KAFKA_HEAP_OPTS" ]]; then
    sed -r -i 's/(export KAFKA_HEAP_OPTS)="(.*)"/\1="'"$KAFKA_HEAP_OPTS"'"/g' "$KAFKA_HOME/bin/kafka-server-start.sh"
    unset KAFKA_HEAP_OPTS
fi

Since the official script kafka-server-start.sh already checks and well handles the environment variable KAFKA_HEAP_OPTS, the block above is redundant. I think it should be removed.

[sscaling]

in every version of kafka that we support? You can raise a PR - but would probably need to add a test case to automatically validate that.