chore(context7): drop the stale planning/ exclusion

The sibling commit on this branch deletes planning/, so the exclusion now
names a directory that does not exist.

Dropping the key rather than leaving an empty list: Context7's schema
(https://context7.com/schema/context7.json) declares no required properties
and gives excludeFolders a default of [], so an absent key and an empty list
are equivalent. Absent matches the repos that never carried the line.

Author: lesnik512

context7.json

@@ -1,5 +1,4 @@
 {
   "url": "https://context7.com/modern-python/httpware",
-  "public_key": "pk_sIP7B0JWZxstxUZb8L28N",
-  "excludeFolders": ["planning"]
+  "public_key": "pk_sIP7B0JWZxstxUZb8L28N"
 }