Mark `SentryEnvelope` as not internal #5375

Job	Run time
system-test (sentry-samples-spring-boot-opentelemetry, true, false)	6m 16s
system-test (sentry-samples-spring-boot-opentelemetry-noagent, false, true)	5m 58s
system-test (sentry-samples-spring-boot-opentelemetry, true, true)	6m 20s
system-test (sentry-samples-spring-boot-jakarta, false, true)	3m 24s
system-test (sentry-samples-spring-boot-jakarta-opentelemetry-noagent, false, true)	6m 23s
system-test (sentry-samples-spring-boot, false, true)	3m 39s
system-test (sentry-samples-spring-boot-webflux, false, true)	3m 37s
system-test (sentry-samples-spring-boot-jakarta-opentelemetry, true, false)	6m 27s
system-test (sentry-samples-spring-boot-jakarta-opentelemetry, true, true)	6m 10s
system-test (sentry-samples-console, false, true)	2m 7s
system-test (sentry-samples-jul, false, true)	1m 57s
system-test (sentry-samples-spring-boot-4-webflux, false, true)	3m 44s
system-test (sentry-samples-log4j2, false, true)	1m 50s
system-test (sentry-samples-spring-boot-webflux-jakarta, false, true)	3m 28s
system-test (sentry-samples-spring-boot-4-opentelemetry, true, false)	6m 18s
system-test (sentry-samples-spring-jakarta, false, true)	3m 8s
system-test (sentry-samples-spring-boot-4-opentelemetry, true, true)	6m 4s
system-test (sentry-samples-logback, false, true)	1m 58s
system-test (sentry-samples-spring, false, true)	3m 16s
system-test (sentry-samples-spring-boot-4, false, true)	3m 5s
	1h 25m 9s

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