Upgrade Dubbo version in sentinel-demo-dubbo

[Leishunyu]

dubbo version change ,old dubbo demo can't import DubboComponentScan on dubbo 2.6.2
I change the version to dubbo 2.6.5

[CLAassistant]

All committers have signed the CLA.

[Leishunyu]

@sczyh30 can you help me review

[codecov-io]

Codecov Report

Merging #436 into master will increase coverage by 0.55%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master     #436      +/-   ##
============================================
+ Coverage     37.69%   38.25%   +0.55%     
- Complexity      981      992      +11     
============================================
  Files           235      235              
  Lines          7409     7409              
  Branches       1016     1016              
============================================
+ Hits           2793     2834      +41     
+ Misses         4254     4204      -50     
- Partials        362      371       +9

Impacted Files	Coverage Δ	Complexity Δ
...a/csp/sentinel/slots/statistic/base/LeapArray.java	68.35% <0%> (+6.32%)	24% <0%> (+2%)	⬆️
...a/csp/sentinel/slots/statistic/base/LongAdder.java	31.91% <0%> (+14.89%)	10% <0%> (+6%)	⬆️
...a/csp/sentinel/slots/statistic/base/Striped64.java	56.25% <0%> (+30.2%)	8% <0%> (+3%)	⬆️

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[sczyh30]

Hi, could you please sign the CLA here: https://cla-assistant.io/alibaba/Sentinel?pullRequest=436

[Leishunyu]

Hi, could you please sign the CLA here: https://cla-assistant.io/alibaba/Sentinel?pullRequest=436

OK,3q

[sczyh30]

LGTM

[sczyh30]

Thanks for contributing!