Revert log level severity for unknown proxy in ForwardedHeadersMiddleware

eng/PatchConfig.props

@@ -49,6 +49,7 @@ Later on, this will be checked using this condition:
   </PropertyGroup>
   <PropertyGroup Condition=" '$(VersionPrefix)' == '2.3.7' ">
     <PackagesInPatch>
+      Microsoft.AspNetCore.HttpOverrides;
     </PackagesInPatch>
   </PropertyGroup>
 </Project>

src/Middleware/HttpOverrides/src/ForwardedHeadersMiddleware.cs

@@ -249,7 +249,7 @@ public void ApplyForwarders(HttpContext context)
                     if (currentValues.RemoteIpAndPort != null && checkKnownIps && !CheckKnownAddress(currentValues.RemoteIpAndPort.Address))
                     {
                         // Stop at the first unknown remote IP, but still apply changes processed so far.
-                        _logger.LogWarning(1, $"Unknown proxy: {currentValues.RemoteIpAndPort}");
+                        _logger.LogDebug(1, $"Unknown proxy: {currentValues.RemoteIpAndPort}");
                         break;
                     }
                 }