Add 2.15.x.rst to toctree

Tagging package [pulp] version [2.14.3-1] in directory [./].

Tagging package [pulp] version [2.14.3-0.1.beta] in directory [./].

Tagging package [pulp] version [2.14.2-1] in directory [./].

Tagging package [pulp] version [2.14.2-0.1.beta] in directory [./].

Tagging package [pulp] version [2.14.1-1] in directory [./].

Tagging package [pulp] version [2.14.1-0.1.beta] in directory [./].

Tagging package [pulp] version [2.13.4-1] in directory [./].

Tagging package [python-kombu] version [3.0.33-8.pulp] in directory […

…deps/python-kombu/].

Tagging package [python-kombu] version [3.0.33-7.pulp] in directory […

…deps/python-kombu/].