remove illuminate/exception replacement (#21734)

as far as I can tell, `illuminate/exception` is no longer provided in the framework.  the subtree has not had an update since 2014.

Author: browner12

composer.json

@@ -52,7 +52,6 @@
         "illuminate/database": "self.version",
         "illuminate/encryption": "self.version",
         "illuminate/events": "self.version",
-        "illuminate/exception": "self.version",
         "illuminate/filesystem": "self.version",
         "illuminate/hashing": "self.version",
         "illuminate/http": "self.version",