Update to new Sphinx theme.

Signed-off-by: Tim 'mithro' Ansell <tansell@google.com>

docs/requirements.txt

diff --git a/docs/requirements.txt b/docs/requirements.txt
index 43d2ef2..056d192 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -1,4 +1,4 @@
-git+https://github.com/SymbiFlow/sphinx_materialdesign_theme.git#egg=sphinx-symbiflow-theme
+git+https://github.com/SymbiFlow/sphinx_symbiflow_theme.git#egg=sphinx-symbiflow-theme
 
 docutils
 sphinx