fix(ingest): Fix oauth config validation in snowflake.

[rslanka]

Fixes the oauth config validation in snowflake config.
It is causing test failures on the CI jobs recently like

• https://github.com/datahub-project/datahub/runs/8124353346?check_suite_focus=true#step:5:2469
• https://github.com/datahub-project/datahub/runs/8123466789?check_suite_focus=true#step:5:3243

Checklist

• The PR conforms to DataHub's Contributing Guideline (particularly Commit Message Format)
• Links to related issues (if applicable)
• Tests for the changes have been added/updated (if applicable)
• Docs related to the changes have been added/updated (if applicable). If a new feature has been added a Usage Guide has been added for the same.
• For any breaking change/potential downtime/deprecation/big changes an entry has been made in Updating DataHub

[github-actions]

Unit Test Results (metadata ingestion)

       8 files  ±0         8 suites  ±0   58m 44s ⏱️ - 1m 1s
   661 tests ±0     658 ✔️ +1  3 💤 ±0  0 ❌  - 1 
1 322 runs  ±0  1 316 ✔️ +2  6 💤 ±0  0 ❌  - 2 

Results for commit d0aebf4. ± Comparison against base commit dbcd309.

[github-actions]

Unit Test Results (build & test)

517 tests  ±0   517 ✔️ +2   8m 10s ⏱️ - 1m 36s
121 suites ±0       0 💤 ±0 
121 files   ±0       0 ❌  - 2 

Results for commit d0aebf4. ± Comparison against base commit dbcd309.