appveyor: partially revert 3413a110 to keep build without proxy

Ref: #5211 and #4526
Reported-by: Marcel Raad
diff --git a/appveyor.yml b/appveyor.yml
index 7e31659..19e37a1 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -192,8 +192,8 @@
       - APPVEYOR_BUILD_WORKER_IMAGE: "Visual Studio 2015"
         BUILD_SYSTEM: autotools
         TESTING: ON
-        DISABLED_TESTS: "~19 ~504 ~704 ~705 ~1056 ~1233 ~1242 ~1243 ~2002 ~2003"
-        CONFIG_ARGS: "--enable-debug --enable-werror --enable-alt-svc --disable-threaded-resolver"
+        DISABLED_TESTS: "~19 ~1056 ~1233 ~1242 ~1243 ~2002 ~2003"
+        CONFIG_ARGS: "--enable-debug --enable-werror --enable-alt-svc --disable-threaded-resolver --disable-proxy"
       - APPVEYOR_BUILD_WORKER_IMAGE: "Visual Studio 2019"
         BUILD_SYSTEM: autotools
         TESTING: ON