disabling 64-bit builds on Appveyor (these started timing out without any changes in PySDM; we do cover 64-bit Windows builds on Github Actions; we still need Appveyor for 32-bit builds)

Author: slayoo

.appveyor.yml

@@ -4,7 +4,7 @@ branches:
 environment:
   matrix:
   - platform: x86
-  - platform: x64
+#  - platform: x64
 
 build: false