The ContextStorageProvider system prop and error message differ

[LaurentTreguier]

Inside of context/src/main/java/io/opentelemetry/context/LazyStorage.java, the io.opentelemetry.context.contextStorageProvider system property is checked for providers.
However, in the IllegalStateExceptions thrown further down in the class, error messages mention the io.opentelemetry.context.ContextStorageProvider property instead (with an uppercase "C" for ContextStorageProvider).

I'm a little bit out of my depth here regarding system property naming, so I'm not sure which one is correct and which one is a typo though

[jkwatson]

I don't think we can really change the system property at this point, so we should consider the message to be wrong. Can you contribute a small PR to fix it? Thanks!

[LaurentTreguier]

Fix proposed in #7342