[rubygems/rubygems] Add missing --prefer-local to Synopsis in bundle-… #1

Job	Run time
cargo test	59s
cargo clippy	41s
make (yjit-bindgen, To fix: use patch in logs, --with-gcc=clang-12 --enable-yjit=dev)	4m 25s
make (check, RUSTC='rustc +1.58.0', 1.58.0)	15m 0s
make (check, --enable-yjit=dev)	19m 57s
make (check, --enable-yjit=dev, --yjit-call-threshold=1 --yjit-verify-ctx --yjit-code-gc)	22m 47s
make (test-bundled-gems, --enable-yjit=dev)	18m 44s
make (yjit-bench, --enable-yjit=dev, --yjit-stats)	5m 29s
YJIT Ubuntu result	1s
	1h 28m 3s

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