Fixes permissions for validate call in github bicep PR flow.

[PabloZaiden]

Add permissions for actions, contents, and security events in workflow.pr.bicep.yml

[github-actions]

🦙 MegaLinter status: ✅ SUCCESS

Descriptor	Linter	Files	Fixed	Errors	Elapsed time
✅ ACTION	actionlint	1		0	0.02s
✅ EDITORCONFIG	editorconfig-checker	1		0	0.02s
✅ REPOSITORY	gitleaks	yes		no	0.1s
✅ SPELL	lychee	1		0	0.02s
✅ YAML	yamllint	1		0	0.27s

See detailed report in MegaLinter reports
Set VALIDATE_ALL_CODEBASE: true in mega-linter.yml to validate all sources, not only the diff

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[github-actions]

Creating environment with name: "638447" using commit: "ddd87c33dd7bc5bcc6a2a00b3348bd1b108e0c16".

The environment will be destroyed after the workflow completes.
To preserve it, add the "preserve-pr-environment" label to the PR.

[github-actions]

E2E Tests Results

12 tests   12 ✔️  1m 21s ⏱️
  1 suites    0 💤
  1 files      0 ❌

Results for commit ddd87c3.