Fix saml related citest failures after gradle shadow plugin upgrade from v8 to v9

[cwperks]

Description

This PR fixes saml related tests failing in ./gradlew :citest

Shadow plugin changelog: https://gradleup.com/shadow/changes/

See v9 migration guide here: https://gradleup.com/shadow/changes/#migration-example

Fixes the following:

Tests with failures:
 - org.opensearch.security.auth.http.saml.HTTPSamlAuthenticatorTest.legacyCommaSeparatedRolesTest
 - org.opensearch.security.auth.http.saml.HTTPSamlAuthenticatorTest.testMetadataBody
 - org.opensearch.security.auth.http.saml.HTTPSamlAuthenticatorTest.testRawHMACSettings
 - org.opensearch.security.auth.http.saml.HTTPSamlAuthenticatorTest.basicTest
 - org.opensearch.security.auth.http.saml.HTTPSamlAuthenticatorTest.shouldNotTrimWhitespaceInJwtRoles
 - org.opensearch.security.auth.http.saml.HTTPSamlAuthenticatorTest.unsolicitedSsoTest
 - org.opensearch.security.auth.http.saml.HTTPSamlAuthenticatorTest.shouldNotEscapeSamlEntities
 - org.opensearch.security.auth.http.saml.HTTPSamlAuthenticatorTest.shouldUnescapeSamlEntitiesTest
 - org.opensearch.security.auth.http.saml.HTTPSamlAuthenticatorTest.basicLogoutTestEncryptedKey
 - org.opensearch.security.auth.http.saml.HTTPSamlAuthenticatorTest.initialConnectionFailureTest
 - org.opensearch.security.auth.http.saml.HTTPSamlAuthenticatorTest.decryptAssertionsTest
 - org.opensearch.security.auth.http.saml.HTTPSamlAuthenticatorTest.idpEndpointWithQueryStringTest
 - org.opensearch.security.auth.http.saml.HTTPSamlAuthenticatorTest.badUnsolicitedSsoTest
 - org.opensearch.security.auth.http.saml.HTTPSamlAuthenticatorTest.rolesTest
 - org.opensearch.security.auth.http.saml.HTTPSamlAuthenticatorTest.noSignatureTest
 - org.opensearch.security.auth.http.saml.HTTPSamlAuthenticatorTest.basicLogoutTest
 - org.opensearch.security.auth.http.saml.HTTPSamlAuthenticatorTest.wrongCertTest
 - org.opensearch.security.auth.http.saml.HTTPSamlAuthenticatorTest.commaSeparatedRolesTest
 - org.opensearch.security.auth.http.saml.HTTPSamlAuthenticatorTest.shouldUnescapeSamlEntitiesTest2
 - org.opensearch.security.auth.http.jwt.keybyoidc.SelfRefreshingKeySetTest.getKeyAfterRefresh_withMultipleCallsShouldIncreaseQueueCount

• Category (Enhancement, New feature, Bug fix, Test fix, Refactoring, Maintenance, Documentation)

Test fix

Issues Resolved

Fixes test failures seen in https://github.com/opensearch-project/security/actions/runs/22202155134/job/64222953670?pr=5963

Check List

• New functionality includes testing
• New functionality has been documented
• New Roles/Permissions have a corresponding security dashboards plugin PR
• API changes companion pull request created
• Commits are signed per the DCO using --signoff

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.85%. Comparing base (708da58) to head (adc182b).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5964      +/-   ##
==========================================
+ Coverage   73.80%   73.85%   +0.04%     
==========================================
  Files         439      439              
  Lines       27086    27086              
  Branches     4018     4018              
==========================================
+ Hits        19992    20004      +12     
+ Misses       5189     5175      -14     
- Partials     1905     1907       +2     

see 12 files with indirect coverage changes

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