.travis.yml in cose-0.10.0 vs .travis.yml in cose-0.11.0

@@ -2,14 +2,13 @@
 language: ruby
 cache: bundler
 
 rvm:
   - ruby-head
-  - 2.7.0-preview3
+  - 2.7.0
   - 2.6.5
   - 2.5.7
   - 2.4.9
-  - 2.3.8
 
 gemfile:
   - gemfiles/openssl_head.gemfile
   - gemfiles/openssl_2_1.gemfile
   - gemfiles/openssl_2_0.gemfile