fix hugegraph-api code checkstyle

[Fizell]

a new PR from #1845
fix only the obvious code style issues :)

[imbajin]

Thanks a lot for quick split

[codecov]

Codecov Report

Merging #1851 (59e641a) into master (85b01b2) will increase coverage by 6.29%.
The diff coverage is 84.61%.

@@             Coverage Diff              @@
##             master    #1851      +/-   ##
============================================
+ Coverage     64.45%   70.75%   +6.29%     
- Complexity      914      982      +68     
============================================
  Files           447      447              
  Lines         38040    38041       +1     
  Branches       5389     5389              
============================================
+ Hits          24520    26915    +2395     
+ Misses        11000     8493    -2507     
- Partials       2520     2633     +113     

Impacted Files	Coverage Δ
.../java/com/baidu/hugegraph/api/auth/ProjectAPI.java	82.05% <ø> (ø)
...va/com/baidu/hugegraph/auth/HugeAuthenticator.java	40.21% <ø> (ø)
...a/com/baidu/hugegraph/license/LicenseVerifier.java	0.00% <0.00%> (ø)
.../java/com/baidu/hugegraph/metrics/MetricsUtil.java	62.50% <66.66%> (ø)
...api/src/main/java/com/baidu/hugegraph/api/API.java	74.11% <70.00%> (-0.89%)	⬇️
.../com/baidu/hugegraph/server/ApplicationConfig.java	93.47% <75.00%> (ø)
...n/java/com/baidu/hugegraph/api/graph/BatchAPI.java	27.41% <85.71%> (ø)
...va/com/baidu/hugegraph/api/gremlin/GremlinAPI.java	75.00% <100.00%> (ø)
...n/java/com/baidu/hugegraph/api/job/GremlinAPI.java	50.72% <100.00%> (ø)
.../com/baidu/hugegraph/api/schema/IndexLabelAPI.java	76.25% <100.00%> (ø)
... and 97 more

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