[spec] Remove sed commands to change mathjax url (#1164)

With the Sphinx upgrade in #1157 we no longer need these sed commands.
At the same time, clean up the way we configure mathjax, using a config
value, instead of sed.

Author: ngzhian

document/core/Makefile

@@ -10,10 +10,6 @@ STATICDIR     = _static
 DOWNLOADDIR   = _download
 NAME          = WebAssembly
 
-# Hack until we have moved to more recent Sphinx.
-OLDMATHJAX    = https://cdn.mathjax.org/mathjax/latest/MathJax.js
-NEWMATHJAX    = https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.1/MathJax.js
-
 # Internal variables.
 PAPEROPT_a4     = -D latex_paper_size=a4
 PAPEROPT_letter = -D latex_paper_size=letter
@@ -111,16 +107,10 @@ html:
 	do \
 	  sed s:BASEDIR:.:g <$$file >$$file.out; \
 	  mv -f $$file.out $$file; \
-	  sed s~$(OLDMATHJAX)~$(NEWMATHJAX)~g <$$file >$$file.out; \
-	  mv -f $$file.out $$file; \
 	done
 	for file in `ls $(BUILDDIR)/html/*/*.html`; \
 	do \
 	  sed s:BASEDIR:..:g <$$file >$$file.out; \
-	  sed 's;<body; <script type="text/javascript">MathJax.Hub.Config({TeX: {MAXBUFFER: 30*1024}})</script><body;' \
-	    <$$file.out >$$file; \
-	  rm -f $$file.out; \
-	  sed s~$(OLDMATHJAX)~$(NEWMATHJAX)~g <$$file >$$file.out; \
 	  mv -f $$file.out $$file; \
 	done
 	@echo

document/core/conf.py

@@ -478,3 +478,9 @@
 rst_prolog = """
 .. include:: /""" + pwd + """/util/macros.def
 """
+
+# https://www.sphinx-doc.org/en/master/usage/extensions/math.html#confval-mathjax_config
+# https://docs.mathjax.org/en/latest/options/input/tex.html#the-configuration-block
+mathjax_config = {
+    'tex': { 'maxBuffer': 30*1024 },
+}