Bump nullaway from 0.7.10 to 0.8.0 (#448)

Bumps [nullaway](https://github.com/uber/NullAway) from 0.7.10 to 0.8.0.
- [Release notes](https://github.com/uber/NullAway/releases)
- [Changelog](https://github.com/uber/NullAway/blob/master/CHANGELOG.md)
- [Commits](uber/NullAway@v0.7.10...v0.8.0)

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

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

Author: dependabot-preview[bot]

build.gradle

@@ -20,7 +20,7 @@ ext.deps = [rxjava2           : 'io.reactivex.rxjava2:rxjava:2.2.19',
             truth             : 'com.google.truth:truth:1.0.1',
             robolectric       : 'org.robolectric:robolectric:4.3.1',
             mockitocore       : 'org.mockito:mockito-core:3.4.4',
-            nullaway          : 'com.uber.nullaway:nullaway:0.7.10',
+            nullaway          : 'com.uber.nullaway:nullaway:0.8.0',
             errorprone        : 'com.google.errorprone:error_prone_core:2.3.4',
             nopen             : 'com.jakewharton.nopen:nopen-annotations:1.0.1',
             nopenchecker      : 'com.jakewharton.nopen:nopen-checker:1.0.1',