Bump third_party/pigweed/repo from `c8c31a0` to `892cd9a` #1066

Job	Run time
Test Suites - Darwin (no-ble-asan-clang)	1h 54m 4s
Test Suites - Linux (no-ble-tsan-clang)	1h 30m 42s
Test Suites - Darwin (no-ble-tsan-clang)	2h 36m 30s
REPL Tests - Darwin	0s
REPL Tests - Linux	32m 50s
	6h 34m 6s

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