Remove tomcat embed dependencies declaration as spring-boot-starter-web has already included them

[zrlw]

What is the purpose of the change?

Remove tomcat embed dependencies declaration from pom.xml of dubbo-parent as

1. spring-boot-starter-web has already included them.
2. dubbo-spring-boot-3-autoconfigure imports spring-boot-dependencies pom which has defined tomcat.version.

Otherwise dependabot[bot]] always try to downgrade the tomcat version of profile spring-boot-3 from 10.x to 9.x, e.g.,

Checklist

• Make sure there is a GitHub_issue field for the change.
• Write a pull request description that is detailed enough to understand what the pull request does, how, and why.
• Write necessary unit-test to verify your logic correction. If the new feature or significant change is committed, please remember to add sample in dubbo samples project.
• Make sure gitHub actions can pass. Why the workflow is failing and how to fix it?

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 60.81%. Comparing base (b54059d) to head (f702b28).

Additional details and impacted files

@@             Coverage Diff              @@
##                3.3   #16173      +/-   ##
============================================
+ Coverage     60.80%   60.81%   +0.01%     
+ Complexity    11767    11751      -16     
============================================
  Files          1953     1953              
  Lines         89118    89118              
  Branches      13444    13444              
============================================
+ Hits          54190    54200      +10     
+ Misses        29367    29357      -10     
  Partials       5561     5561              

Flag	Coverage Δ
integration-tests-java21	32.16% <ø> (-0.01%)	⬇️
integration-tests-java8	32.18% <ø> (-0.07%)	⬇️
samples-tests-java21	32.15% <ø> (-0.03%)	⬇️
samples-tests-java8	29.83% <ø> (+0.11%)	⬆️
unit-tests-java11	59.02% <ø> (-0.02%)	⬇️
unit-tests-java17	58.52% <ø> (+0.02%)	⬆️
unit-tests-java21	58.53% <ø> (-0.01%)	⬇️
unit-tests-java25	58.48% <ø> (-0.02%)	⬇️
unit-tests-java8	59.00% <ø> (-0.07%)	⬇️

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