Fix RumSessionEnded metric flaky test

[ambushwork]

What does this PR do?

Fix the min boundary of generating the int for unit test.

Review checklist (to be filled by reviewers)

• [ ] Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• [ ] Make sure you discussed the feature or bugfix with the maintaining team in an Issue
• [ ] Make sure each commit and the PR mention the Issue number (cf the CONTRIBUTING doc)

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 69.67%. Comparing base (d2a5741) to head (15e7882). Report is 13 commits behind head on develop.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #2114 +/- ## =========================================== - Coverage 69.84% 69.67% -0.17% =========================================== Files 715 715 Lines 26577 26590 +13 Branches 4457 4458 +1 =========================================== - Hits 18561 18525 -36 - Misses 6821 6838 +17 - Partials 1195 1227 +32 ``` [see 28 files with indirect coverage changes](https://app.codecov.io/gh/DataDog/dd-sdk-android/pull/2114/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=DataDog)