fix(eslint): '@typescript-eslint/explicit-function-return-… (#4872)

.eslintrc.js

lib/datasource/docker/index.ts

lib/datasource/github/index.ts

lib/datasource/gitlab/index.ts

lib/datasource/index.ts

lib/datasource/maven/util.ts

lib/datasource/metadata.ts

lib/datasource/npm/get.ts

lib/datasource/npm/npmrc.ts

lib/datasource/nuget/v2.ts

lib/datasource/nuget/v3.ts

lib/datasource/packagist/index.ts

lib/datasource/pypi/index.ts

lib/datasource/rubygems/get-rubygems-org.ts

lib/datasource/rubygems/get.ts

lib/datasource/rubygems/retriable.ts

lib/datasource/sbt/index.ts

lib/datasource/sbt/util.ts

lib/datasource/terraform/index.ts

lib/logger/pretty-stdout.ts