Updated new onboarding criteria (#5337)

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check off every point from the Essential Checklist! -->
## Explanation
Updated new onboarding criteria because sometimes 2 PRs can be small
changes. And sometimes the contributor does not communicate well and
will disappear soon. With that we see more new contributors so that we
can keep growing the team, under the stricter acceptance criteria.

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- Explain what your PR does. If this PR fixes an existing bug, please
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- "Fixes #bugnum:" in the explanation so that GitHub can auto-close the
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## Essential Checklist
<!-- Please tick the relevant boxes by putting an "x" in them. -->
- [ ] The PR title and explanation each start with "Fix #bugnum: " (If
this PR fixes part of an issue, prefix the title with "Fix part of
#bugnum: ...".)
- [ ] Any changes to
[scripts/assets](https://github.com/oppia/oppia-android/tree/develop/scripts/assets)
files have their rationale included in the PR explanation.
- [x] The PR follows the [style
guide](https://github.com/oppia/oppia-android/wiki/Coding-style-guide).
- [x] The PR does not contain any unnecessary code changes from Android
Studio
([reference](https://github.com/oppia/oppia-android/wiki/Guidance-on-submitting-a-PR#undo-unnecessary-changes)).
- [x] The PR is made from a branch that's **not** called "develop" and
is up-to-date with "develop".
- [x] The PR is **assigned** to the appropriate reviewers
([reference](https://github.com/oppia/oppia-android/wiki/Guidance-on-submitting-a-PR#clarification-regarding-assignees-and-reviewers-section)).

---------

Co-authored-by: Adhiambo Peres <59600948+adhiamboperes@users.noreply.github.com>

wiki/Contributing-to-Oppia-Android.md

@@ -53,7 +53,7 @@ When you've found an issue you'd like to tackle:
 
 You are also welcome to tackle non-starter issues, but for those, you might need to be more independent, because we might not know how to solve them either!
 
-Once you've merged PRs that correspond to **two** different pre-existing GitHub issues, please fill in [this form](https://forms.gle/NxPjimCMqsSTNUgu5) to become an Oppia collaborator! This will grant you access to the repository, and allow you to join a team. (But please don't create your own issues and then make PRs for them -- that won't count.)
+Once you've merged PRs that correspond to **two** different pre-existing GitHub issues, please fill in [this form](https://forms.gle/NxPjimCMqsSTNUgu5) to be considered for a place on a team at Oppia Android! A team lead will evaluate your contributions and give you access to the repository so that you can assign yourself to issues. (But please don't create your own issues and then make PRs for them -- that won't count.)