Remove the remaining closure in the src/core/function.js file

Given that the code is written with JavaScript module-syntax, none of this functionality will "leak" outside of this file with these changes.
By removing this closure the file-size is decreased, even for the *built* `pdf.worker.js` file, since there's now less overall indentation in the code.

src/core/function.js

@@ -815,13 +815,6 @@ class PostScriptEvaluator {
   }
 }
 
-// Most of the PDFs functions consist of simple operations such as:
-//   roll, exch, sub, cvr, pop, index, dup, mul, if, gt, add.
-//
-// We can compile most of such programs, and at the same moment, we can
-// optimize some expressions using basic math properties. Keeping track of
-// min/max values will allow us to avoid extra Math.min/Math.max calls.
-const PostScriptCompiler = (function PostScriptCompilerClosure() {
 class AstNode {
   constructor(type) {
     this.type = type;
@@ -1061,7 +1054,12 @@ const PostScriptCompiler = (function PostScriptCompilerClosure() {
   return new AstMin(num1, max);
 }
 
-  // eslint-disable-next-line no-shadow
+// Most of the PDFs functions consist of simple operations such as:
+//   roll, exch, sub, cvr, pop, index, dup, mul, if, gt, add.
+//
+// We can compile most of such programs, and at the same moment, we can
+// optimize some expressions using basic math properties. Keeping track of
+// min/max values will allow us to avoid extra Math.min/Math.max calls.
 class PostScriptCompiler {
   compile(code, domain, range) {
     const stack = [];
@@ -1246,9 +1244,6 @@ const PostScriptCompiler = (function PostScriptCompilerClosure() {
   }
 }
 
-  return PostScriptCompiler;
-})();
-
 export {
   isPDFFunction,
   PDFFunctionFactory,