Update default versions to OpenMRS Core 2.8.4 and RefApp 3.6.0 (#109)

Remove -SNAPSHOT suffix from the default openmrs.version (2.8.4) and
refapp.version (3.6.0) properties in pom.xml so the standalone build
targets the released versions.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: dkayiwa

pom.xml

@@ -21,8 +21,8 @@
 		<liquibase.plugin.version>4.23.2</liquibase.plugin.version>
 
 		<tomcat.version>9.0.106</tomcat.version>
-		<openmrs.version>2.8.4-SNAPSHOT</openmrs.version>
-		<refapp.version>3.6.0-SNAPSHOT</refapp.version>
+		<openmrs.version>2.8.4</openmrs.version>
+		<refapp.version>3.6.0</refapp.version>
 		<mariadb4jVersion>3.2.0</mariadb4jVersion>
 		<junitVersion>5.12.2</junitVersion>
 		<mockitoVersion>3.12.4</mockitoVersion>