Set MeetupSizeTarget to 15 #754

Job	Run time
build	4m 22s
build-try-runtime-and-benchmarks	5m 44s
Build Runtimes (encointer-node-notee)	3m 15s
Cancel Previous Runs	4s
cargo-toml-fmt	12s
Rust check +nightly fmt --all -- --check (x86_64-unknown-linux-gnu)	25s
unit-tests	2m 28s
Rust check clippy -p encointer-client-notee (x86_64-unknown-linux-gnu)	5m 35s
test_bootstrap_demo_community.sh	18m 48s
test_bot_community.sh	7m 45s
test_register_business.sh	2m 10s
Draft Release	0s
Publish Runtimes	0s
	50m 48s

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