Update version codes to prepare for RC02 of Beta MR2 (oppia#4745)

## Explanation
Updates version codes for RC02 of Beta MR2 (since cherry-picks were
needed).

## Essential Checklist
- [ ] ~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: ...".)~
- [x] 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".
- [ ] ~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)).~

## For UI-specific PRs only
N/A -- This is an infrastructural change that doesn't affect the user
experience.

version.bzl

@@ -10,10 +10,10 @@ MAJOR_VERSION = 0
 MINOR_VERSION = 10
 
 # TODO(#4419): Remove the Kenya-specific alpha version code.
-OPPIA_DEV_KITKAT_VERSION_CODE = 41
-OPPIA_DEV_VERSION_CODE = 42
-OPPIA_ALPHA_KITKAT_VERSION_CODE = 43
-OPPIA_ALPHA_VERSION_CODE = 44
-OPPIA_ALPHA_KENYA_VERSION_CODE = 45
-OPPIA_BETA_VERSION_CODE = 46
-OPPIA_GA_VERSION_CODE = 47
+OPPIA_DEV_KITKAT_VERSION_CODE = 48
+OPPIA_DEV_VERSION_CODE = 49
+OPPIA_ALPHA_KITKAT_VERSION_CODE = 50
+OPPIA_ALPHA_VERSION_CODE = 51
+OPPIA_ALPHA_KENYA_VERSION_CODE = 52
+OPPIA_BETA_VERSION_CODE = 53
+OPPIA_GA_VERSION_CODE = 54