Fix example value for max-message-size

[falko]

@npepinpe once told me to use zeebe.client.message.max-message-size=4194304, which sounds like the default value and seems to be in bytes. If we use a too small example value, users may think the value is in megabytes. Obviously, we could also just document the unit but even then 3 bytes is likely not a workable value.

Description

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[github-actions]

👋 🤖 🤔 Hello, @falko! Did you make your changes in all the right places?

These files were changed only in docs/. You might want to duplicate these changes in versioned_docs/version-8.6/.

• docs/apis-tools/spring-zeebe-sdk/configuration.md

You may have done this intentionally, but we wanted to point it out in case you didn't. You can read more about the versioning within our docs in our documentation guidelines.