KNOX-2167 - Upgrade frontend-maven-plugin to 1.9.1

Signed-off-by: Kevin Risden <krisden@apache.org>
diff --git a/gateway-admin-ui/pom.xml b/gateway-admin-ui/pom.xml
index 001726d..333a7b2 100644
--- a/gateway-admin-ui/pom.xml
+++ b/gateway-admin-ui/pom.xml
@@ -30,7 +30,7 @@
     <description>The gateway-admin-ui delivered with Knox.</description>
 
     <properties>
-        <frontend-maven-plugin.version>1.8.0</frontend-maven-plugin.version>
+        <frontend-maven-plugin.version>1.9.1</frontend-maven-plugin.version>
         <nodejs.version>v10.16.0</nodejs.version>
     </properties>