Bump third_party/pigweed/repo from `9640cde` to `acad217` #1079

Job	Run time
REPL Tests - Linux	35m 38s
Test Suites - Darwin (no-ble-asan-clang)	1h 30m 11s
Test Suites - Linux (no-ble-tsan-clang)	1h 32m 57s
Test Suites - Darwin (no-ble-tsan-clang)	2h 6m 46s
REPL Tests - Darwin	0s
	5h 45m 32s

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