Remove redundant \lbrack and \rbrack (#1416)

* Remove redundant \lbrack and \rbrack

* Revert macros. Remove redundant code.

* Revert symbols

src/delimiter.js

@@ -219,12 +219,12 @@ const makeStackedDelim = function(
         top = "\\Uparrow";
         repeat = "\u2016";
         bottom = "\\Downarrow";
-    } else if (delim === "[" || delim === "\\lbrack") {
+    } else if (delim === "[") {
         top = "\u23a1";
         repeat = "\u23a2";
         bottom = "\u23a3";
         font = "Size4-Regular";
-    } else if (delim === "]" || delim === "\\rbrack") {
+    } else if (delim === "]") {
         top = "\u23a4";
         repeat = "\u23a5";
         bottom = "\u23a6";
@@ -480,7 +480,7 @@ const makeSqrtImage = function(
 // There are three kinds of delimiters, delimiters that stack when they become
 // too large
 const stackLargeDelimiters = [
-    "(", ")", "[", "\\lbrack", "]", "\\rbrack",
+    "(", ")", "[", "]",
     "\\{", "\\lbrace", "\\}", "\\rbrace",
     "\\lfloor", "\\rfloor", "\u230a", "\u230b",
     "\\lceil", "\\rceil", "\u2308", "\u2309",

src/functions/delimsizing.js

@@ -35,7 +35,7 @@ const delimiterSizes = {
 };
 
 const delimiters = [
-    "(", ")", "[", "\\lbrack", "]", "\\rbrack",
+    "(", ")", "[", "]",
     "\\{", "\\lbrace", "\\}", "\\rbrace",
     "\\lfloor", "\\rfloor", "\u230a", "\u230b",
     "\\lceil", "\\rceil", "\u2308", "\u2309",