Unify naming; update MRI to 2.7.3

Author: pitr-ch

.travis.yml

@@ -7,18 +7,20 @@ matrix:
   fast_finish: true
   include:
     # Latest versions first
-    - name: MRI 2.7.0 Latest
-      rvm: 2.7.0
+    - name: Latest MRI 2.7.3
+      rvm: 2.7.3
     - name: Latest JRuby 9.2.18.0 on Java 11
       rvm: jruby-9.2.18.0
       jdk: oraclejdk11
     - name: Latest JRuby 9.2.18.0 on Java 8
       rvm: jruby-9.2.18.0
       jdk: openjdk8
-    - name: TruffleRuby Latest
+    - name: Latest TruffleRuby
       rvm: truffleruby
+
+    # Documentation up-to-date check
     - name: YARD uptodate in docs
-      rvm: 2.7.0
+      rvm: 2.7.3
       script:
       - bundle install --with documentation
       - bundle exec rake yard:master:uptodate