fix(generators)!: Make scrub_ public

Fixes google#2156.

In PRs google#7602, google#7616, google#7646, google#7647 and google#7654 the @Protected
access modifier on scrub_ on the CodeGenerator subclasses
was not transcribed to the new typescript signature.  I was
going to re-add it, but this breaks some of the procedure
block generator functions which rely on it, and then
@BeksOmega pointed out that this might be one of the
CodeGenerator API functions which we had already decided
should be public—and lo and behold I found google#2156.

Per discussion amongst team, I am not renaming it to
scrub at this time.

core/generator.ts

@@ -568,7 +568,7 @@ export class CodeGenerator {
    * @param _opt_thisOnly True to generate code for only this statement.
    * @returns Code with comments and subsequent blocks added.
    */
-  protected scrub_(
+  scrub_(
     _block: Block,
     code: string,
     _opt_thisOnly?: boolean,

generators/javascript/javascript_generator.ts

@@ -251,7 +251,6 @@ export class JavascriptGenerator extends CodeGenerator {
    * @param code The JavaScript code created for this block.
    * @param thisOnly True to generate code for only this statement.
    * @returns JavaScript code with comments and subsequent blocks added.
-   * @protected
    */
   scrub_(block: Block, code: string, thisOnly = false): string {
     let commentCode = '';

generators/python/python_generator.ts

@@ -276,7 +276,6 @@ export class PythonGenerator extends CodeGenerator {
    * @param code The Python code created for this block.
    * @param thisOnly True to generate code for only this statement.
    * @returns Python code with comments and subsequent blocks added.
-
    */
   scrub_(block: Block, code: string, thisOnly = false): string {
     let commentCode = '';