Update sphinx from 1.8.3 to 1.8.4

requirements/docs.txt

@@ -9,9 +9,9 @@ Pygments==2.3.1 \
     --hash=sha256:e8218dd399a61674745138520d0d4cf2621d7e032439341bc3f647bff125818d \
     --hash=sha256:5ffada19f6203563680669ee7f53b64dabbeb100eb51b61996085e99c03b284a
 # Sphinx is required by sphinxcontrib-httpdomain
-Sphinx==1.8.3 \
-    --hash=sha256:429e3172466df289f0f742471d7e30ba3ee11f3b5aecd9a840480d03f14bcfe5 \
-    --hash=sha256:c4cb17ba44acffae3d3209646b6baec1e215cad3065e852c68cc569d4df1b9f8
+Sphinx==1.8.4 \
+    --hash=sha256:b53904fa7cb4b06a39409a492b949193a1b68cc7241a1a8ce9974f86f0d24287 \
+    --hash=sha256:c1c00fc4f6e8b101a0d037065043460dffc2d507257f2f11acaed71fd2b0c83c
 # alabaster is required by Sphinx
 alabaster==0.7.12 \
     --hash=sha256:446438bdcca0e05bd45ea2de1668c1d9b032e1a9154c2c259092d77031ddd359 \