Revert "Add hotjar tracking script (#184)" (#264)

This reverts commit 73607ce, given that
we've decided not to use the product. Saves users some loading time by
loading one js less and one external request less.

Author: stefano-ottolenghi

src/partials/head-hotjar.hbs

@@ -1,6 +1,5 @@
 {{> head-prelude}}
 {{> head-gtm}}
-{{> head-hotjar}}
 {{> head-title}}
 {{> head-info}}
 {{> head-styles}}