Update information about image tagsin the README

The project does not rely on any underlying versioning to dictate the version
used in its image tags. The README is updated to reflect that state of affairs.

README.md

@@ -156,10 +156,9 @@ want set:
 
 ## Image tags ##
 
-The images of this container are tagged with [semantic
-versions](https://semver.org) of the underlying example project that they
-containerize.  It is recommended that most users use a version tag (e.g.
-`:0.0.3`).
+The images of this container are tagged with
+[semantic versions](https://semver.org).  It is recommended that most users use
+a version tag (e.g. `:0.0.3`).
 
 | Image:tag | Description |
 |-----------|-------------|