Tests

Bump third_party/jsoncpp/repo from `69098a1` to `8214f71` #990

Job	Run time
REPL Tests - Darwin	0s
REPL Tests - Linux	6m 21s
Test Suites - Darwin (no-ble-asan-clang)	7m 41s
Test Suites - Darwin (no-ble-tsan-clang)	7m 15s
Test Suites - Linux (no-ble-tsan-clang)	5m 43s
	27m 0s

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