[FLINK-18532][docs] Remove beta tag from MATCH_RECOGNIZE

[sjwiesman]

What is the purpose of the change

Removes the beta tag from MATCH_RECOGNIZE and updates the note to better reflect community priorities.

Brief change log

• Update docs

Verifying this change

This change is a trivial rework/code cleanup without any test coverage.

Does this pull request potentially affect one of the following parts:

• no

Documentation

• Does this pull request introduce a new feature? (yes / no)
• If yes, how is the feature documented? (not applicable / docs / JavaDocs / not documented)

[sjwiesman]

@dawidwys I updated the note about limitations to better communicate how the community is prioritizing match recognize features. WDYT? Also, any concerns with me backporting this to 1.11?

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Last check on commit 0da7c38 (Mon Jul 13 15:33:03 UTC 2020)

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CI report:

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[dawidwys]

+1. Thank you for updating it!

[dawidwys]

I am also fine with backporting it to 1.11

[sjwiesman]

TY, merging . . .