Revert "Check highlight tags before replacing them (#82)" (#84)

This reverts commit b761550.

Author: curquiza

src/format.js

@@ -5,11 +5,7 @@ function replaceHighlightTags(value, highlightPreTag, highlightPostTag) {
   // If the value of the attribute is a string,
   // the highlight is applied by MeiliSearch (<em> tags)
   // and we replace the <em> by the expected tag for InstantSearch
-  if (
-    isString(value) &&
-    highlightPreTag !== undefined &&
-    highlightPostTag !== undefined
-  ) {
+  if (isString(value)) {
     newHighlightValue = value
       .replace(/<em>/g, highlightPreTag)
       .replace(/<\/em>/g, highlightPostTag)