Update parent pom to 2.1.11, add relativePath tag

relativePath prevents Maven from searching locally for the parent pom,
forcing it to go to the standard Maven repositories.

Author: ch-tstrickland

pom.xml

@@ -6,7 +6,8 @@
     <parent>
         <groupId>uk.gov.companieshouse</groupId>
         <artifactId>companies-house-parent</artifactId>
-        <version>2.1.6</version>
+        <version>2.1.11</version>
+        <relativePath/>
     </parent>
     <artifactId>orders.api.ch.gov.uk</artifactId>
     <version>unversioned</version>