docs: add code fences to `Example:` docstring blocks (#2104) #823

Job	Run time
checks / pre-commit	31s
checks / readme-snippets	11s
checks / test (3.11, lowest-direct, ubuntu-latest)	1m 2s
checks / test (3.11, lowest-direct, windows-latest)	2m 26s
checks / test (3.12, locked, ubuntu-latest)	54s
checks / test (3.10, lowest-direct, windows-latest)	2m 26s
checks / test (3.11, locked, windows-latest)	2m 25s
checks / test (3.12, lowest-direct, windows-latest)	3m 28s
checks / test (3.13, locked, windows-latest)	2m 23s
checks / test (3.11, locked, ubuntu-latest)	51s
checks / test (3.13, lowest-direct, ubuntu-latest)	51s
checks / test (3.13, locked, ubuntu-latest)	48s
checks / test (3.14, locked, ubuntu-latest)	2m 27s
checks / test (3.14, lowest-direct, windows-latest)	2m 17s
checks / test (3.14, locked, windows-latest)	3m 7s
checks / test (3.12, locked, windows-latest)	3m 16s
checks / test (3.10, locked, windows-latest)	2m 29s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 16s
checks / test (3.10, locked, ubuntu-latest)	51s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 1s
checks / test (3.13, lowest-direct, windows-latest)	2m 24s
checks / test (3.10, lowest-direct, ubuntu-latest)	55s
all-green	3s
	38m 22s

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