[spec] Fix Katex hacks 3

Author: rossberg

document/core/util/mathjax2katex.py

@@ -61,7 +61,7 @@ def HasBalancedTags(s):
 
 def ReplaceMath(cache, data):
   old = data
-  data = re.sub('[\\\\]\\[([0-9]|-)', '\\\\\\\\DOUBLESLASH\\[\\1', data)  # Messed up by Bikeshed
+  data = re.sub('[\\\\][\\\\]\\[([0-9]|-)', '\\\\DOUBLESLASH[\\1', data)  # Messed up by Bikeshed
   data = data.replace('\\\\', '\\DOUBLESLASH')
   #data = data.replace('\\(', '')
   #data = data.replace('\\)', '')