docs: fix invalid anchor links in DESIGN_GUIDELINES (#31292)

Fix invalid anchor links in [DESIGN_GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md).

### Checklist
- [x] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: mazyu36

docs/DESIGN_GUIDELINES.md

@@ -31,7 +31,7 @@ experience across the entire AWS surface area.
     * [Dropped Mutations](#dropped-mutations)
   * [Factories](#factories)
   * [Imports](#imports)
-    * [“from” Methods](#-from--methods)
+    * [“from” Methods](#from-methods)
     * [From-attributes](#from-attributes)
   * [Roles](#roles)
   * [Resource Policies](#resource-policies)
@@ -55,8 +55,8 @@ experience across the entire AWS surface area.
     * [Error reporting mechanism](#error-reporting-mechanism)
     * [Throwing exceptions](#throwing-exceptions)
     * [Never Catch Exceptions](#never-catch-exceptions)
-    * [Attaching (lazy) Validators](#attaching--lazy--validators)
-    * [Attaching Errors/Warnings](#attaching-errors-warnings)
+    * [Attaching (lazy) Validators](#attaching-lazy-validators)
+    * [Attaching Errors/Warnings](#attaching-errorswarnings)
     * [Error messages](#error-messages)
   * [Tokens](#tokens)
 * [Documentation](#documentation)