Replace error handling in GetRemote with try

[bep]

See #9797

Unfortunately this is hard to deprecate. Fortunately the breakage will be loud and should be simple to fix. So for the example in docs:

{{ $url := "https://example.org/images/a.jpg" }}
{{ with resources.GetRemote $url }}
  {{ with .Err }}
    {{ errorf "%s" . }}
  {{ else }}
    <img src="{{ .RelPermalink }}" width="{{ .Width }}" height="{{ .Height }}" alt="">
  {{ end }}
{{ else }}
  {{ errorf "Unable to get remote resource %q" $url }}
{{ end }}

Will need to be rewritten to:

{{ $url := "https://example.org/images/a.jpg" }}
{{ with try (resources.GetRemote $url) }}
  {{ with .Err }}
    {{ errorf "%s" . }}
  {{ else with .Value }}
    <img src="{{ .RelPermalink }}" width="{{ .Width }}" height="{{ .Height }}" alt="">
  {{ else }}
      {{ errorf "Unable to get remote resource %q" $url }}
  {{ end }}
{{ end }}