[actions] update workbench docker version to v0.2.7 (#1124)

Co-authored-by: erinmgraham <3822277+erinmgraham@users.noreply.github.com>

Author: carpentries-bot

.github/workbench-docker-version.txt

@@ -1 +1 @@
-v0.2.4
+v0.2.7