Update openmrs core version to 2.7.3

Author: dkayiwa

distro/pom.xml

@@ -25,7 +25,7 @@
          we do so here so that we can utilise Maven to track updates, etc. -->
     <fhir2.version>2.4.0-SNAPSHOT</fhir2.version>
     <authentication.version>1.1.0</authentication.version>
-    <openmrs.version>2.7.2</openmrs.version>
+    <openmrs.version>2.7.3</openmrs.version>
     <initializer.version>2.9.0</initializer.version>
     <webservices.rest.version>2.49.0-SNAPSHOT</webservices.rest.version>
     <addresshierarchy.version>2.20.0</addresshierarchy.version>