content/static/html/helpers: add space to Deprecated banner

Add a space after the colon in "Deprecated: reason".

For golang/go#41321

Change-Id: I2440c4cc34ec23d4e7eb81e926d815013ff32725
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/307489
Trust: Jonathan Amsterdam <jba@google.com>
Run-TryBot: Jonathan Amsterdam <jba@google.com>
Reviewed-by: Jamal Carvalho <jamal@golang.org>
diff --git a/content/static/html/helpers/_unit_header.tmpl b/content/static/html/helpers/_unit_header.tmpl
index 1e5b2fe..5f3282b 100644
--- a/content/static/html/helpers/_unit_header.tmpl
+++ b/content/static/html/helpers/_unit_header.tmpl
@@ -207,7 +207,7 @@
         <span class="Site-margin UnitHeader-bannerContent">
           <strong>Deprecated</strong>
           {{with .Unit.DeprecationComment}}
-            <strong>:</strong> {{.}}
+            <strong>:</strong>&nbsp;{{.}}
           {{end}}
         </span>
       </div>