[type:fix] fix plugin can not load resource path file

[misaya295]

and pr apache/shenyu-dashboard#383.

Make sure that:

• You have read the contribution guidelines.
• You submit test cases (unit or integration tests) that back your changes.
• Your local test passed ./mvnw clean install -Dmaven.javadoc.skip=true.

[codecov-commenter]

Codecov Report

Attention: 24 lines in your changes are missing coverage. Please review.

Comparison is base (d93d6b7) 61.56% compared to head (6100edf) 61.56%.
Report is 1 commits behind head on master.

Files	Patch %	Lines
.../org/apache/shenyu/web/loader/PluginJarParser.java	0.00%	15 Missing ⚠️
...che/shenyu/web/loader/ShenyuPluginClassLoader.java	0.00%	9 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #5372   +/-   ##
=========================================
  Coverage     61.56%   61.56%           
- Complexity     8519     8522    +3     
=========================================
  Files          1236     1236           
  Lines         37296    37313   +17     
  Branches       3591     3593    +2     
=========================================
+ Hits          22961    22973   +12     
- Misses        12253    12257    +4     
- Partials       2082     2083    +1     

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