Convert template to US-ASCII to fix error

I introduced some tests in a feature branch to match the contents of
`/etc/nginx/router_routes.conf`. They worked fine when run with `bundle exec
rake spec` or `bundle exec rspec modules/router/spec`. But when run as
`bundle exec rake` each should block failed with:

    ArgumentError:
      invalid byte sequence in US-ASCII

I eventually found that removing the `.with_content(//)` matchers made the
errors go away. That there weren't any weird characters in the spec file. And
that it could be reproduced by requiring Puppet in the same interpreter with:

    rake -E 'require "puppet"' spec

That particular template appears to be the only file in our codebase with an
identified encoding of `utf-8`. All others are `us-ascii`:

    dcarley-MBA:puppet dcarley$ find modules -type f -exec file --mime {} \+ | grep utf
    modules/router/templates/routes.conf.erb:                                         text/plain; charset=utf-8

Attempting to convert that file back to US-ASCII identified the offending
character as something that looked like a whitespace:

    dcarley-MBA:puppet dcarley$ iconv -f UTF8 -t US-ASCII modules/router/templates/routes.conf.erb 2>&1 | tail -n5
      proxy_intercept_errors off;

      # Set proxy timeout to 50 seconds as a quick fix for problems
      #
    iconv: modules/router/templates/routes.conf.erb:458:3: cannot convert

After replacing it (by hand) the file identifies as `us-ascii` again:

    dcarley-MBA:puppet dcarley$ file --mime modules/router/templates/routes.conf.erb
    modules/router/templates/routes.conf.erb: text/plain; charset=us-ascii

Now the tests work! One hour of my life I won't get back..

modules/router/templates/routes.conf.erb

@@ -460,7 +460,7 @@ location ~ ^/apply-for-a-licence/? {
   proxy_intercept_errors off;
 
   # Set proxy timeout to 50 seconds as a quick fix for problems
-  # where civica QueryPayments calls are taking too long.
+  # where civica QueryPayments calls are taking too long.
   proxy_read_timeout 50;
   proxy_pass http://varnish;
 }