rails_52.gemfile in instana-1.209.3

- old
+ new

@@ -11,9 +11,10 @@
 gem "webmock"
 gem "puma"
 gem "rubocop", "~> 1.9"
 gem "rack-test"
 gem "simplecov", "~> 0.21.2"
+gem "mail", "< 2.8.0"
 gem "rails", ">= 5.2", "< 6.0"
 gem "mysql2", "0.4.10"
 gem "pg"
 gem "sqlite3", "~> 1.3", "< 1.4"
 