Delete dead links and add warning about an outdated section

docs/software/repository-management.md

@@ -32,7 +32,10 @@ These repos are updated by the `kojira` daemon running on `koji.opensciencegrid.
 Build repositories
 ------------------
 
-The `koji` task in `osg-build` uses the [osg-3.4-el6-build](http://koji.opensciencegrid.org/koji/taginfo?tagID=472)/[osg-3.4-el7-build](http://koji.opensciencegrid.org/koji/taginfo?tagID=481) repo, which is the union of the following repositories:
+!!! warning
+    this section is out of date; the tags it references no longer exist.
+
+The `koji` task in `osg-build` uses the osg-3.4-el6-build/osg-3.4-el7-build repo, which is the union of the following repositories:
 
 -   Minefield a.k.a. `osg-3.4-el6-development` / `osg-3.4-el7-development`
 -   The `osg-el6-internal` / `osg-el7-internal` tag (containing build dependencies we do not want to make public)
@@ -41,7 +44,7 @@ The `koji` task in `osg-build` uses the [osg-3.4-el6-build](http://koji.openscie
 
 Koji will work from its internal cache of the above repositories (downloading the packages from the source), and will not update until the build repository is regenerated. By default, Koji does a groupinstall of the build group, then resolves the BuildRequires dependencies.
 
-The tarball creation scripts use the [osg-3.4-el6-release-build](https://koji.opensciencegrid.org/koji/taginfo?tagID=478) / [osg-3.4-el7-release-build](https://koji.opensciencegrid.org/koji/taginfo?tagID=487) repo, which is the union of the following repositories:
+The tarball creation scripts use the osg-3.4-el6-release-build / osg-3.4-el7-release-build repo, which is the union of the following repositories:
 
 -   Release a.k.a. `osg-3.4-el6-release` / `osg-3.4-el7-release`
 -   The `dist-el6-build` / `dist-el7-build` tag (consisting of the appropriate macros for `%dist`)