remove some not very useful update events (#1486)

[sre-bot]

cherry-pick #1486 to release-1.1

---

What problem does this PR solve?

fixes: #1471
Now, there are too many SuccessfulUpdate events emitted by tidb-operator, but they are not very useful.

	// by default, allow a source to send 25 events about an object
	// but control the refill rate to 1 new event every 5 minutes
	// this helps control the long-tail of events for things that are always
	// unhealthy
	defaultSpamBurst = 25
	defaultSpamQPS   = 1. / 300.
)

record.Event method in client-go has a spamFilter which is responsible for throttling
the amount of events a source and object can produce.

So we'd better remove these not very useful SuccessfulUpdate events.

What is changed and how does it work?

Check List

Tests

• Unit test

Code changes

• Has Go code change

Side effects

Related changes

• Need to cherry-pick to the release branch
• Need to update the documentation

Does this PR introduce a user-facing change?:

Remove some not very useful update events

[onlymellb]

LGTM

[cofyc]

/merge

[sre-bot]

Your auto merge job has been accepted, waiting for 1405, 1501, 1493, 1491

[sre-bot]

/run-all-tests