Bumps plugin pom from 4.66 to 4.67. (#1466)

https://github.com/jenkinsci/plugin-pom/releases/tag/plugin-4.67 provides
more details of the changes, including:

* Fix hamcrest versioning - @timja
  https://github.com/jenkinsci/plugin-pom/issues/785

* Update HtmlUnit package for jacoco - @timja
  https://github.com/jenkinsci/plugin-pom/issues/778

pom.xml

@@ -5,7 +5,7 @@
   <parent>
     <groupId>org.jenkins-ci.plugins</groupId>
     <artifactId>plugin</artifactId>
-    <version>4.66</version>
+    <version>4.67</version>
     <relativePath />
   </parent>