Updating the docs to match latest skywater-pdk.

Taken from https://github.com/google/skywater-pdk
```
commit b5ff6174d9aa921f670f12a2893969fe4a516f6c (HEAD -> main, upstream/main)
Merge: 5e159bd 73e9c84
Author: Tim Ansell <me@mith.ro>
Date:   Tue Nov 2 13:28:11 2021 -0700

    Merge pull request #341 from mithro/sphinx-theme-fix

    Update the sphinx theme
```

Signed-off-by: Tim 'mithro' Ansell <tansell@google.com>
diff --git a/docs/requirements.txt b/docs/requirements.txt
index 6ffa95d..b585a69 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -1,16 +1,22 @@
-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
 sphinx-autobuild
+
 # Verilog domain
 sphinx-verilog-domain
 # Verilog diagrams using Yosys + netlistsvg
 sphinxcontrib-hdl-diagrams
+
 # Module diagrams
 git+https://github.com/SymbiFlow/symbolator.git#egg=symbolator
 git+https://github.com/hdl/pyHDLparser.git#egg=hdlparse
+
 # pycairo
 # vext.gi
+
 restructuredtext-lint
 rstdoc
+
 tabulate