Added notes for the default charset and collation in the default conf…

[xtcyclist]

…ig file.

What type of PR is this?

• bug
• feature
• enhancement

What problem(s) does this PR solve?

Issue(s) number:

Close https://github.com/vesoft-inc/nebula-ent/issues/1934
Close #5065

Description:

How do you solve it?

Special notes for your reviewer, ex. impact of this fix, design document, etc:

Checklist:

Tests:

• Unit test(positive and negative cases)
• Function test
• Performance test
• N/A

Affects:

• Documentation affected (Please add the label if documentation needs to be modified.)
• Incompatibility (If it breaks the compatibility, please describe it and add the label.）
• If it's needed to cherry-pick (If cherry-pick to some branches is required, please label the destination version(s).)
• Performance impacted: Consumes more CPU/Memory

Release notes:

Please confirm whether to be reflected in release notes and how to describe:

ex. Fixed the bug .....

[codecov-commenter]

Codecov Report

Base: 77.24% // Head: 77.32% // Increases project coverage by +0.08% 🎉

Coverage data is based on head (1834aa4) compared to base (cc0ce34).
Patch coverage: 83.48% of modified lines in pull request are covered.

❗ Current head 1834aa4 differs from pull request most recent head 57782f2. Consider uploading reports for the commit 57782f2 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5066      +/-   ##
==========================================
+ Coverage   77.24%   77.32%   +0.08%     
==========================================
  Files        1105     1105              
  Lines       82054    82137      +83     
==========================================
+ Hits        63383    63515     +132     
+ Misses      18671    18622      -49     

Impacted Files	Coverage Δ
src/graph/executor/admin/ShowHostsExecutor.cpp	93.54% <ø> (+0.99%)	⬆️
src/graph/executor/query/ProjectExecutor.cpp	61.11% <ø> (-2.78%)	⬇️
src/graph/optimizer/Optimizer.h	100.00% <ø> (ø)
src/graph/service/QueryInstance.cpp	80.13% <50.00%> (-0.56%)	⬇️
src/graph/validator/MatchValidator.cpp	89.51% <75.00%> (-0.08%)	⬇️
src/graph/executor/query/TraverseExecutor.cpp	84.90% <82.06%> (+16.88%)	⬆️
src/graph/executor/query/TraverseExecutor.h	90.00% <86.95%> (-10.00%)	⬇️
src/graph/optimizer/Optimizer.cpp	92.80% <95.00%> (+0.76%)	⬆️
src/common/expression/PropertyExpression.cpp	92.41% <100.00%> (+0.44%)	⬆️
src/meta/processors/parts/GetSpaceProcessor.cpp	61.29% <0.00%> (-19.36%)	⬇️
... and 36 more

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