[CM] Remove maximum timeout value for request network

The request network with timeout was originally created with a
check of max timeout against a constant of 100 minutes. However,
the API was not public and did not implement a timeout. Any users
were internal and never got any onUnavailable() callback (since
timeout never triggered).

There is no reason to have a max timeout so the constant is
remove.

Bug: 31399536
Test: unit tests and CTS of ConnectivityManager
Change-Id: Icbedfb4299d75b6a7e3e43720111531f1faafd06