appveyor path fix2

.appveyor.yml

@@ -1,8 +1,8 @@
 environment:
   RUST_BACKTRACE: 1
-  OPENSSL_DIR "C:\Tools\vcpkg\packages\openssl-windows_x64-windows"
+  OPENSSL_DIR: C:\Tools\vcpkg\packages\openssl-windows_x64-windows
-  BSON_LIB "C:\Tools\vcpkg\packages\libbson_x64-windows\lib"
+  BSON_LIB: C:\Tools\vcpkg\packages\libbson_x64-windows\lib
-  MONGO_LIB "C:\Tools\vcpkg\packages\mongo-c-driver_x64-windows\lib"
+  MONGO_LIB: C:\Tools\vcpkg\packages\mongo-c-driver_x64-windows\lib
   matrix:
   - TARGET: x86_64-pc-windows-msvc
 install: