fix template syntax and url (#752)

Author: Chris Cho

docs/reference/themes/mongodb/layouts/partials/header.html

@@ -25,6 +25,6 @@
               <div class="documentwrapper">
                 <div class="bodywrapper">
                   <div class="body">
-                    {{ if ( findRE ".*mongo-java-driver\/4.3\/(?!apidocs)" .URL ) }}
+                    {{ if ( and ( findRE ".*mongo-java-driver/4.3/driver/" .URL ) ( not ( findRE ".*/apidocs/.*" .URL ))) }}
                       {{- partial "header/newSiteNotice.html" . -}}
                     {{ end }}

docs/reference/themes/mongodb/layouts/partials/header/newSiteNotice.html

@@ -1,6 +1,6 @@
 <div style="padding: 15px; margin: 20px 0px; border-width: 1px 1px 1px 0px; border-style: solid; border-radius: 6px; font-size: 14px; line-height: 20px; color: rgb(17, 97, 73); border-color: rgb(195, 231, 202) rgb(195, 231, 202) rgb(195, 231, 202) rgb(19, 170, 82); background-color: rgb(228, 244, 228);">
   This reference documentation site is for versions of the MongoDB Java synchronous driver up to 4.3-beta.
   <br/>
-  See the <a style="font-weight: bold" href="https://docs.mongodb.com/drivers/java/sync/current">MongoDB Java Driver documentation site</a> for version 4.3 and later versions of the reference documentation.
+  See the <a style="font-weight: bold" href="https://docs.mongodb.com/drivers/java/sync/current/">MongoDB Java Driver documentation site</a> for version 4.3 and later versions of the reference documentation.
 </div>