fix(ingest): continue validation of s3 path_specs even if platform is set

[mayurinehate]

Issue reported on Slack

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 (build & test)

521 tests  ±0   515 ✔️ ±0   14m 16s ⏱️ +3s
122 suites ±0       0 💤 ±0 
122 files   ±0       6 ❌ ±0 

For more details on these failures, see this check.

Results for commit dff72ec. ± Comparison against base commit 66985335.

[github-actions]

Unit Test Results (metadata ingestion)

       8 files  ±0         8 suites  ±0   57m 34s ⏱️ + 1m 20s
   707 tests ±0     704 ✔️ +1  3 💤 ±0  0 ❌  - 1 
1 414 runs  ±0  1 408 ✔️ +1  6 💤 ±0  0 ❌  - 1 

Results for commit dff72ec. ± Comparison against base commit 66985335.