Lengthen the demo signing keys in the identity-assertion examples #3669

Job	Run time
checks / readme-snippets	14s
checks / pre-commit	51s
checks / docs	1m 6s
checks / test (3.10, lowest-direct, windows-latest)	1m 50s
checks / test (3.11, lowest-direct, windows-latest)	2m 2s
checks / test (3.11, locked, ubuntu-latest)	1m 22s
checks / test (3.10, locked, windows-latest)	1m 49s
checks / test (3.10, locked, ubuntu-latest)	1m 19s
checks / test (3.12, lowest-direct, windows-latest)	1m 55s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 8s
checks / test (3.10, lowest-direct, ubuntu-latest)	1m 30s
checks / test (3.13, locked, windows-latest)	1m 53s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 20s
checks / test (3.11, lowest-direct, ubuntu-latest)	1m 27s
checks / test (3.14, lowest-direct, windows-latest)	1m 53s
checks / test (3.12, locked, ubuntu-latest)	1m 44s
checks / test (3.12, locked, windows-latest)	1m 54s
checks / test (3.14, locked, windows-latest)	2m 1s
checks / test (3.14, locked, ubuntu-latest)	1m 19s
checks / test (3.11, locked, windows-latest)	1m 54s
checks / test (3.13, lowest-direct, ubuntu-latest)	1m 24s
checks / test (3.13, locked, ubuntu-latest)	1m 13s
checks / test (3.13, lowest-direct, windows-latest)	2m 4s
all-green	2s
	35m 14s

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