Linux topic example consistency (#18568)

aspnetcore/host-and-deploy/linux-nginx/nginx.conf

@@ -7,7 +7,7 @@ http {
     keepalive_timeout   29; # Adjust to the lowest possible value that makes sense for your use case.
     client_body_timeout 10; client_header_timeout 10; send_timeout 10;
 
-    upstream hellomvc{
+    upstream helloapp{
         server localhost:5000;
     }
 
@@ -37,7 +37,7 @@ http {
 
         #Redirects all traffic
         location / {
-            proxy_pass http://hellomvc;
+            proxy_pass http://helloapp;
             limit_req  zone=one burst=10 nodelay;
         }
     }