Best Practices claim Migration in C8 unsupported but it is

[falko]

Process Instance Migration is supported in C8 therefore the Best Practices need updating:

https://github.com/camunda/camunda-docs/blob/60178187659c87a71bb1377097ceba7a24ef3957/versioned_docs/version-8.5/components/best-practices/operations/versioning-process-definitions.md?plain=1#L36-L38

[akeller]

@johanwelgemoed, can you look at this? How can we position how process instance migration works in C8 compared to what we have written for C7?

If it's too complicated or time-consuming, I could see the following as a quick win:

• Adjust the admonition to link to C8 docs on process instance migration
• Remove indications that it's not supported or in development
• Add backlog issue for updating Best Practice section to compare C7 vs. C8 process instance migration

[korthout]

Opened #3986 for some quick wins and opened #3987 to track the follow-up work.