Bump third_party/pigweed/repo from `9504c03` to `fbb318a` #1069

Job	Run time
REPL Tests - Linux	40m 44s
Test Suites - Darwin (no-ble-asan-clang)	1h 13m 25s
Test Suites - Darwin (no-ble-tsan-clang)	1h 40m 11s
Test Suites - Linux (no-ble-tsan-clang)	1h 33m 55s
REPL Tests - Darwin	0s
	5h 8m 15s

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