[fix] simple theme: adjust image detail height

when on the top of the page, the image is just below the search fields.
this commit slightly aligh the top of the image detail with the bottom
of the search fields.

searx/static/themes/simple/src/less/definitions.less

@@ -219,7 +219,7 @@
 @result-padding: 1rem;
 @search-width: 40rem;
 // heigh of #search, see detail.less
-@search-height: 7.5rem;
+@search-height: 7.75rem;
 
 /// Device Size
 /// @desktop > @tablet