Chore: update irmago to v0.15.0 #798

Job	Run time
lint	2m 26s
unit-test	1m 29s
build-irmagobridge-ios	6m 45s
build-irmagobridge-android	2m 47s
build-prototypes-android	6m 5s
build-app-android (alpha, apk)	6m 50s
build-integration-test-android	6m 14s
build-app-android (alpha, appbundle)	5m 50s
build-app-android (beta, apk)	6m 48s
build-app-android (beta, appbundle)	5m 48s
build-integration-test-ios	12m 7s
build-app-ios-alpha	9m 37s
integration-test-android	25m 55s
integration-test-ios	22m 12s
	2h 0m 53s

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