fix(generators): Improve consistency of migrated language generators (#7662)

* docs(generators): @fileoverview -> @file; delete @suppress

* fix(generators): Fix return type of getAdjusted

  And improve its documentation too.

  Fix the @returns doc for PythonGenerator's getAdjustedInt but
  (for now) don't change the type because it does actually
  return numbers in some circumstances.

generators/javascript/javascript_generator.ts

@@ -295,7 +295,7 @@ export class JavascriptGenerator extends CodeGenerator {
    * @param delta Value to add.
    * @param negate Whether to negate the value.
    * @param order The highest order acting on this value.
-   * @returns The adjusted value.
+   * @returns The adjusted value or code that evaluates to it.
    */
   getAdjusted(
     block: Block,
@@ -303,7 +303,7 @@ export class JavascriptGenerator extends CodeGenerator {
     delta = 0,
     negate = false,
     order = Order.NONE,
-  ): string | number {
+  ): string {
     if (block.workspace.options.oneBasedIndex) {
       delta--;
     }