text: set font style to em nested in blockquote

* Sets the em font style to normal when it's nested in a blockquote as
  the blockquote font style is already italic.

Co-Authored-by: iGor milhit <igor@milhit.ch>

assets/scss/_texts.scss

@@ -45,6 +45,10 @@
       margin: .4rem 0;
     }
 
+    em {
+        font-style: normal;
+    }
+
     figcaption {
       text-align: right;
       margin-top: 1rem;