chore: add openvpn to experimental suite #344

Job	Run time
Ensure the code builds (OoniStableFullRelease)	3m 0s
Ensure the code builds (OoniStableFdroidRelease)	2m 20s
Ensure the code builds (DwStableFullRelease)	2m 40s
Ensure the code builds (DwStableFdroidRelease)	2m 22s
Run unit tests	2m 41s
Archive APKs (OoniStableFullDebug)	1m 49s
Run instrumented tests (25, default)	4m 41s
Archive APKs (OoniStableFdroidDebug)	2m 12s
Run instrumented tests (25, google_apis)	4m 40s
Archive APKs (OoniDevFullDebug)	2m 18s
Archive APKs (OoniDevFullDebugAndroidTest)	3m 52s
Run instrumented tests (29, default)	4m 42s
Archive APKs (DwStableFullDebug)	1m 53s
Run instrumented tests (29, google_apis)	4m 36s
Archive APKs (DwStableFdroidDebug)	1m 41s
Archive APKs (DwDevFullDebug)	2m 28s
Upload artifact to Firebase App Distribution	0s
	47m 55s

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