fix evergreen script.

Author: imlucas

.evergreen.yml

@@ -84,7 +84,7 @@ functions:
         curl -fs \
           -o "signtool.exe" \
           --url "https://s3.amazonaws.com/boxes.10gen.com/build/signtool.exe"
-        rm node_modules/electron-installer-squirrel-windows/vendor/signtool.exe
+        rm -f node_modules/electron-installer-squirrel-windows/vendor/signtool.exe
 
   # Environment variables set for use by notary-service signtool.exe on Windows:
   # NOTARY_URL, NOTARY_AUTH_TOKEN, NOTARY_SIGNING_KEY, NOTARY_SIGNING_COMMENT