fix syntax error

Author: devalog

_pages/books.md

@@ -15,7 +15,7 @@ permalink: /books/
 {% endfor %}
 
   <!-- Regular book posts (excluding pinned ones) -->
-{% assign regular_book_posts = site.posts | where_exp: "post", "post.tags contains 'books' and post.pinned != true" %}
+{% assign regular_book_posts = site.posts | where_exp: "post", "post.tags contains \"books\" and post.pinned != true" %}
 {% for post in regular_book_posts %}
   <article>
     <small>

_pages/tech.md

@@ -15,7 +15,7 @@ permalink: /tech/
 {% endfor %}
 
   <!-- Regular tech posts (excluding pinned ones) -->
-{% assign regular_tech_posts = site.posts | where_exp: "post", "post.tags contains 'tech' and post.pinned != true" %}
+{% assign regular_tech_posts = site.posts | where_exp: "post", "post.tags contains \"tech\" and post.pinned != true" %}
 {% for post in regular_tech_posts %}
   <article>
     <small>