jsonnet: fix unicode quotes in jsonnet to avoid tools failing to pars…

…e it properly (#11716)

**What this PR does / why we need it**:
We have a linter in place in our internal deployment tooling to catch
the usage of Unicode quotes because it has caused some issues due to
shells/tooling not recognizing them. The linter has caught one such
instance in the jsonnet in the Loki repo, which is fixed in this PR.

production/ksonnet/loki/gateway.libsonnet

@@ -48,7 +48,7 @@ local k = import 'ksonnet-util/kausal.libsonnet';
 
           server {
             listen               80;
-            auth_basic           “Prometheus”;
+            auth_basic           "Prometheus";
             auth_basic_user_file /etc/nginx/secrets/.htpasswd;
             proxy_set_header     X-Scope-OrgID %(gateway_tenant_id)s;