pref: default code block indentation from Tab to 2 Spaces in editor

[LIlGG]

What type of PR is this?

/kind improvement
/area editor
/milestone 2.17.x

What this PR does / why we need it:

将默认编辑器中代码块的缩进由一个制表符(\t)，更改为两个空格 {2}。

How to test it?

测试使用 Tab 即 Shift + Tab 缩进时，是否每次缩进两个空格而不是一个制表符。

Does this PR introduce a user-facing change?

优化默认编辑器代码块缩进为两个空格。

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 56.45%. Comparing base (5fdf6c0) to head (9f6f073).
Report is 235 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #6090      +/-   ##
============================================
- Coverage     56.91%   56.45%   -0.46%     
- Complexity     3319     3540     +221     
============================================
  Files           587      623      +36     
  Lines         18968    20956    +1988     
  Branches       1401     1478      +77     
============================================
+ Hits          10795    11831    +1036     
- Misses         7594     8525     +931     
- Partials        579      600      +21     

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[ruibaby]

/lgtm

[ruibaby]

/approve

[f2c-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

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