[IMP] theme_bookstore: correct snippet title hierarchy for SEO

For SEO and accessibility reasons, this commit replaces incorrect
heading elements (hX) with appropriate hierarchy in snippet lacking
proper structure.

task-5231498

Author: duau-odoo

theme_bookstore/views/snippets/s_key_images.xml

@@ -12,19 +12,19 @@
         Finely hand-picked by our most avid readers
     </xpath>
     <xpath expr="//div[hasclass('col-lg-3')]//p[3]" position="replace">
-        <h5>Boundless</h5>
+        <h3 class="h5-fs">Boundless</h3>
         <p class="text-muted">by <em>Frantzou Fleurine</em></p>
     </xpath>
     <xpath expr="(//div[hasclass('col-lg-3')])[2]//p[3]" position="replace">
-        <h5>Romans</h5>
+        <h3 class="h5-fs">Romans</h3>
         <p class="text-muted">by <em>Steve Backwood</em></p>
     </xpath>
     <xpath expr="(//div[hasclass('col-lg-3')])[3]//p[3]" position="replace">
-        <h5>101 Essays That Will Change the Way You Think</h5>
+        <h3 class="h5-fs">101 Essays That Will Change the Way You Think</h3>
         <p class="text-muted">by <em>Brianna Wiest</em></p>
     </xpath>
     <xpath expr="(//div[hasclass('col-lg-3')])[4]//p[3]" position="replace">
-        <h5>What I Didn't Post On Instagram</h5>
+        <h3 class="h5-fs">What I Didn't Post On Instagram</h3>
         <p class="text-muted">by <em>Chrissy Stockton</em></p>
     </xpath>
 </template>