docs: fixes for yaml frontmatter (#1851)

Co-authored-by: Subhrodip Mohanta <hello@subho.xyz>

filterer/README.md

@@ -3,10 +3,8 @@ layout: pattern
 title: Filterer
 folder: filterer
 permalink: /patterns/filterer/
-description: Design pattern that helps container-like objects to return filtered version of themselves.# short meta description that shows in Google search results
 language: en
-categories:
- - Functional
+categories: Functional
 tags:
  - Extensibility
 ---