Remove vestigial comment in advancedSymbols.js TeX backslash control sequences are letters-only, whereas HTML character entity references are alphanumeric; therefore `&there4;` is a valid character entity reference, but `\there4` cannot be a valid control sequence. Initially I hoped to support every character entity reference as a backslash command, but we can't support this one, so forget it. The out-of-place "case" is because backslash commands used to be a switch/case, not a dictionary: https://github.com/mathquill/mathquill/commit/77bd6c476f081979c6ea754ece77eff783f3c928#diff-239c238d8c090904fa1a9261bf2ef674L961

diff --git a/src/commands/math/advancedSymbols.js b/src/commands/math/advancedSymbols.js
index b7240aa..3ce1318 100644
--- a/src/commands/math/advancedSymbols.js
+++ b/src/commands/math/advancedSymbols.js

@@ -16,7 +16,7 @@
 
 LatexCmds['∗'] = LatexCmds.ast = LatexCmds.star = LatexCmds.loast = LatexCmds.lowast =
   bind(BinaryOperator,'\\ast ','&lowast;');
-  //case 'there4 = // a special exception for this one, perhaps?
+
 LatexCmds.therefor = LatexCmds.therefore =
   bind(BinaryOperator,'\\therefore ','&there4;');