Fix a typo in appveyor.yml

appveyor.yml

@@ -2,7 +2,7 @@
 
   global:
     # SDK v7.0 MSVC Express 2008's SetEnv.cmd script will fail if the
-    # /E:ON and /V:ON options are not enabled in the batch script intepreter
+    # /E:ON and /V:ON options are not enabled in the batch script interpreter
     # See: http://stackoverflow.com/a/13751649/163740
     WITH_COMPILER: "cmd /E:ON /V:ON /C .\\appveyor\\run_with_env.cmd"