style: add missing brackets and remove unused including headers

[SYaoJun]

Reason for this PR

fix some style problems, including single line statements without brackets and unused header files.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 36.36364% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.60%. Comparing base (b21da29) to head (55cb062).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
cpp/src/graphar/high-level/graph_reader.h	12.50%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##               main     #914   +/-   ##
=========================================
  Coverage     80.60%   80.60%           
  Complexity      615      615           
=========================================
  Files            94       94           
  Lines         10709    10710    +1     
  Branches       1055     1055           
=========================================
+ Hits           8632     8633    +1     
  Misses         1837     1837           
  Partials        240      240           

Flag	Coverage Δ
cpp	70.91% <36.36%> (+<0.01%)	⬆️

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