#1361 Sloeber won't install

Try with http category update sites
Instead of https, try with http update site
Remove redundant update sites

Author: wimjongman

io.sloeber.updatesite/category.xml

@@ -16,9 +16,5 @@
          Only select this if you are upgrading the Sloeber IDE
       </description>
    </category-def>
-   <repository-reference location="https://download.eclipse.org/releases/latest/" enabled="true" />
-   <repository-reference location="https://download.eclipse.org/eclipse/updates/latest" enabled="true" />
-   <repository-reference location="https://download.eclipse.org/justj/jres/15/updates/release/latest/" enabled="true" />
-   <repository-reference location="https://download.eclipse.org/technology/babel/update-site/latest/" enabled="true" />
-   <repository-reference location="https://download.eclipse.org/nebula/releases/latest/" enabled="true" />
+   <repository-reference location="http://download.eclipse.org/nebula/releases/latest" enabled="true" />
 </site>