rustup: update to `nightly-2025-06-23` (~1.89). #654

Job	Run time
cargo-deny	1m 8s
Lint	6m 15s
Android (ubuntu-24.04, aarch64-linux-android)	8m 18s
Compiletest (macOS-latest)	7m 26s
Difftest (macOS-latest)	8m 24s
Compiletest (windows-2022)	15m 36s
Test (ubuntu-24.04)	7m 55s
Compiletest (ubuntu-24.04)	8m 31s
Test (windows-2022)	14m 21s
Difftest (windows-2022)	17m 27s
Difftest (ubuntu-24.04)	9m 46s
Test (macOS-latest)	5m 31s
test_success	3s
	1h 50m 41s

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