Set main branch as dependabot target #2896

Job	Run time
cross-targets (x86_64-sun-solaris)	1m 4s
cross-tests (ubuntu-latest)	1m 49s
check-docs	24s
alternative_targets (ubuntu-latest, wasm32-unknown-emscripten)	32s
alternative_targets (ubuntu-latest, aarch64-apple-ios)	18s
features_check (ubuntu-latest)	5m 59s
no_std (ubuntu-latest, thumbv6m-none-eabi)	13s
rust_msrv (ubuntu-latest)	1m 30s
alternative_targets (ubuntu-latest, aarch64-linux-android)	10s
features_check (macos-latest)	11m 36s
no_std (ubuntu-latest, x86_64-fortanix-unknown-sgx)	43s
features_check (windows-latest)	9m 51s
test_wasi (ubuntu-latest, wasm32-wasi)	25s
rust_versions (ubuntu-latest, stable)	1m 26s
rust_versions (ubuntu-latest, beta)	1m 14s
test_wasm (ubuntu-latest)	32s
rust_versions (ubuntu-latest, nightly)	1m 19s
timezones (ubuntu-latest, ACST-9:30)	1m 21s
timezones (ubuntu-latest, EST4)	1m 30s
timezones (ubuntu-latest, UTC0)	1m 17s
timezones (ubuntu-latest, Asia/Katmandu)	1m 26s
timezones (macos-latest, ACST-9:30)	1m 26s
timezones (macos-latest, EST4)	56s
timezones (macos-latest, UTC0)	52s
timezones (macos-latest, Asia/Katmandu)	1m 7s
timezones (windows-latest, ACST-9:30)	1m 27s
timezones (windows-latest, EST4)	1m 59s
timezones (windows-latest, UTC0)	2m 43s
timezones (windows-latest, Asia/Katmandu)	2m 17s
	57m 26s

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