Bump libraryVersion.retrofit2 from 2.4.0 to 2.7.1

Bumps `libraryVersion.retrofit2` from 2.4.0 to 2.7.1.

Updates `retrofit` from 2.4.0 to 2.7.1
- [Release notes](https://github.com/square/retrofit/releases)
- [Changelog](https://github.com/square/retrofit/blob/master/CHANGELOG.md)
- [Commits](square/retrofit@parent-2.4.0...parent-2.7.1)

Updates `adapter-rxjava2` from 2.4.0 to 2.7.1

Updates `converter-gson` from 2.4.0 to 2.7.1

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Author: dependabot-preview[bot]

app-v3/build.gradle

@@ -60,7 +60,7 @@ ext {
     libraryVersion = [
             support        : '28.0.0',
             gson           : '2.8.6',
-            retrofit2      : '2.4.0',
+            retrofit2      : '2.7.1',
             circleimageview: '2.1.0',
             dagger         : '2.18',
             glassfish      : '10.0-b28',