Fix ISM e2e tests for OS 2.9: conditional toast dismiss and flexible column count

[aditi-1601]

Description

Fixes index-management-e2e (test_e2e_ism) failures on OpenSearch 2.9

• managed_indices_spec.js: replace unconditional toast dismiss calls with a
  conditional dismiss so the spec doesn't fail when no toast is present

• transforms_spec.js: match the "columns hidden" link with a flexible regex instead of the hard-coded "50 columns hidden", so the
  test is resilient to the column count rendered by the UI

Issues Resolved

[List any issues this PR will resolve]

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🧪 No relevant tests

🔒 No security concerns identified

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🔀 Multiple PR themes Sub-PR theme: Conditional toast dismiss in managed_indices_spec Relevant files: cypress/integration/plugins/index-management-dashboards-plugin/managed_indices_spec.js Sub-PR theme: Flexible columns-hidden regex in transforms_spec Relevant files: cypress/integration/plugins/index-management-dashboards-plugin/transforms_spec.js

⚡ No major issues detected

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PR Code Suggestions ✨

Explore these optional code suggestions:

Category	Suggestion	Impact
General	Anchor regex to avoid unintended matches Using cy.contains with a regex like /\d+ columns hidden/ may match unintended elements containing digits followed by " columns hidden" substring anywhere on the page. Anchor the regex to ensure it matches the full expected phrase, e.g. /^\d+ columns hidden$/, to avoid flaky matches against overlapping text nodes. cypress/integration/plugins/index-management-dashboards-plugin/transforms_spec.js [105] -cy.contains(/\d+ columns hidden/).click({ force: true }); +cy.contains(/^\d+ columns hidden$/).click({ force: true }); Suggestion importance[1-10]: 4 __ Why: Anchoring the regex is a reasonable minor improvement for matching precision, but the original pattern is likely sufficient in this context and the impact is low.	Low