doc: sync eol confluence versions

Confluence versions before 7.14 have reached end-of-life and will not be
tested in next release cycle system tests; updating to the oldest
version supported.

Signed-off-by: James Knight <[email protected]>

Author: jdknight

doc/conf.py

@@ -13,7 +13,7 @@
 version = sphinxcontrib.confluencebuilder.__version__
 release = sphinxcontrib.confluencebuilder.__version__
 
-supported_confluence_ver = '7.13+'
+supported_confluence_ver = '7.14+'
 supported_python_ver = '3.7+'
 supported_sphinx_ver = '5.3+'