Revert "Use SourceForge CDN for CI"

This reverts commit 8cd2066.

Author: ivankravets

platform.py

@@ -12,24 +12,11 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from os import getenv
-
 from platformio.managers.platform import PlatformBase
 
 
 class Espressif8266Platform(PlatformBase):
 
-    @property
-    def package_repositories(self):
-        repositories = super(
-            Espressif8266Platform, self).package_repositories or []
-        if getenv("CI", "false").lower() == "true":
-            repositories = [
-                "https://sourceforge.net/projects/platformio-storage/"
-                "files/packages/manifest.json"
-            ] + repositories
-        return repositories
-
     def configure_default_packages(self, variables, targets):
         if not variables.get("pioframework"):
             self.packages['sdk-esp8266']['optional'] = False