fix(ingestion): tighten conditions for restli json transformation

[hsheth2]

Uses startswith instead of find and limits the replace to one modification.

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)

[github-actions]

Unit Test Results (build & test)

  45 files  ±0    45 suites  ±0   11m 7s ⏱️ - 3m 4s
505 tests ±0  449 ✔️ ±0  56 💤 ±0  0 ❌ ±0 

Results for commit 9f8ff31. ± Comparison against base commit cec541d.

♻️ This comment has been updated with latest results.

[github-actions]

Unit Test Results (metadata ingestion)

       5 files  ±0         5 suites  ±0   32m 13s ⏱️ - 4m 46s
   274 tests ±0     272 ✔️  - 1    0 💤 ±0  2 ❌ +1 
1 261 runs  +2  1 231 ✔️ +7  28 💤  - 6  2 ❌ +1 

For more details on these failures, see this check.

Results for commit 9f8ff31. ± Comparison against base commit cec541d.

♻️ This comment has been updated with latest results.

[shirshanka]

LGTM