Remove @aws-crypto/ie11-detection dependency

[lucasmcdonald3]

What

Remove dependency on @aws-crypto/ie11-detection from ESDK-JS web-crypto-backend module.

Why

• Package was deleted from GitHub in 2023 but still published on npm
• ESDK-JS should not depend on a package that will never be updated
• IE11 was officially end-of-life by Microsoft in June 2022

Changes

• Removed @aws-crypto/ie11-detection dependency from package.json
• Removed IE11 code paths from backend-factory.ts and synchronous_random_values.ts
• Deleted promisify-ms-crypto.ts (IE11-specific file)
• Removed IE11-specific tests and fixtures
• 8 files changed, 8 insertions(+), 249 deletions(-)

Test Evidence

• ✅ All 20 mocha unit tests pass
• ✅ TypeScript compilation successful
• ✅ Linting passes (eslint + prettier)

Breaking Change

This completely removes IE11 support from the web-crypto-backend module. Modern browsers with standard WebCrypto API are now required.

Risks and Mitigations

• Risk: IE11 users will lose functionality
• Mitigation: IE11 has been EOL since June 2022, usage is <0.35% globally
• Risk: Breaking change for existing users
• Mitigation: Will be released as major version bump (5.0.0)