Use HTTPS instead of HTTP to resolve dependencies

This fixes a security vulnerability in this project where the `pom.xml`
files were configuring Maven to resolve dependencies over HTTP instead of
HTTPS.

Signed-off-by: Jonathan Leitschuh <[email protected]>

Author: JLLeitschuh

opengrok-web/pom.xml

@@ -268,7 +268,7 @@ Portions Copyright (c) 2018, Chris Fraire <[email protected]>.
         <pluginRepository>
             <name>oss.sonatype.org</name>
             <id>oss.sonatype.org</id>
-            <url>http://oss.sonatype.org/content/groups/public</url>
+            <url>https://oss.sonatype.org/content/groups/public</url>
         </pluginRepository>
     </pluginRepositories>