Fix styles and instructions in docs

[calvinxiao]

1. Make command to create MySQL user consistent across docs and init.sql
2. Remove markdown syntax in code blocks
3. Fix some markdown style problems

Why?
Improve docs quality

How did you test it?
No tests required

Potential risks
No

Release notes

Documentation Changes

[CLAassistant]

All committers have signed the CLA.

[longquanzheng]

It should be fine but just want to check, do you know what's the differences? It seems like All is more than .

[longquanzheng]

And also what difference it makes for 'uber'@'%'?

[calvinxiao]

1. GRANT ALL PRIVILEGES TO 'uber'@'%'; without ON *.* doesn't work on MySQL8.0 via docker, I know I should've used 5.7. For people didn't read all the full documentation, docker pull mysql will pull 8.* version.
2. The host name part of the account name, if omitted, defaults to '%'., I just copied them from /docs/setup/MYSQL_SETUP.md and /docker/buildkite/mysql-init/init.sql, so they look the same.

[longquanzheng]

Just two comments about information. The PR LGTM. Thanks for fixing them!

[coveralls]

Pull Request Test Coverage Report for Build 9f53da8d-0b95-4b11-be23-3ac08cc589bd

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 126 unchanged lines in 12 files lost coverage.
• Overall coverage decreased (-0.05%) to 60.22%

---

Files with Coverage Reduction	New Missed Lines	%
common/persistence/executionStore.go	2	75.75%
common/persistence/statsComputer.go	2	96.43%
common/persistence/serialization/parser.go	4	69.32%
common/persistence/serialization/thrift_decoder.go	4	63.44%
common/task/fifoTaskScheduler.go	5	82.47%
service/history/queue/processor_base.go	7	61.82%
service/history/shard/context.go	8	65.83%
common/persistence/sql/workflowStateMaps.go	12	83.12%
common/persistence/serialization/getters.go	16	60.69%
service/history/execution/context.go	17	68.39%

Totals
Change from base Build bcd1b045-6c8d-4f71-a965-6277827d7a0f:	-0.05%
Covered Lines:	88869
Relevant Lines:	147574

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💛 - Coveralls