Update index.html.erb

Fix typo

Author: alanmaddrell

source/index.html.erb

@@ -87,7 +87,7 @@ description: GOV.UK Pay is for central government, local authorities, police and
         <div class="govuk-grid-column-one-half">
           <h2 class="content-section__title govuk-heading-m">Or use GOV.UK&nbsp;Pay’s API in your digital service</h2>
           <p class="govuk-body">
-            We also have an API so you can seamslessly
+            We also have an API so you can seamlessly
             <%= link_to 'integrate GOV.UK&nbsp;Pay into your full digital service.', 'api-integration', class: 'govuk-link' %>
           </p>
           <p class="govuk-body">The API is based on REST principles with endpoints returning data in JSON format. Our API lets you:</p>