[MINOR] docs: correct the format of server_guide doc

[zuston]

What changes were proposed in this pull request?

correct the format of server_guide doc

Why are the changes needed?

The markdown format is wrong in original shuffle server guide doc

Does this PR introduce any user-facing change?

No

How was this patch tested?

Dont need

[zuston]

I hope this could be included in version 0.7. PTAL @kaijchen

[codecov-commenter]

Codecov Report

Merging #608 (a4e7f39) into master (80c12a7) will increase coverage by 2.29%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master     #608      +/-   ##
============================================
+ Coverage     60.85%   63.15%   +2.29%     
- Complexity     1800     1801       +1     
============================================
  Files           214      200      -14     
  Lines         12387    10416    -1971     
  Branches       1044     1044              
============================================
- Hits           7538     6578     -960     
+ Misses         4444     3494     -950     
+ Partials        405      344      -61     

Impacted Files	Coverage Δ
...y/kubernetes/operator/pkg/webhook/inspector/pod.go
deploy/kubernetes/operator/pkg/utils/config.go
deploy/kubernetes/operator/pkg/utils/rss.go
...rnetes/operator/pkg/webhook/inspector/inspector.go
deploy/kubernetes/operator/pkg/utils/certs.go
...eploy/kubernetes/operator/pkg/utils/coordinator.go
...oy/kubernetes/operator/pkg/utils/shufflerserver.go
...oy/kubernetes/operator/pkg/controller/util/util.go
...bernetes/operator/pkg/controller/controller/rss.go
...y/kubernetes/operator/pkg/webhook/inspector/rss.go
... and 5 more

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[kaijchen]

LGTM, thanks @zuston.