Revert "Require \r whitespace to be followed by \n"

[dtolnay]

Revert #393. It turns out bare \r is only prohibited inside of literals. In between tokens, bare \r is allowed and equivalent to \n.

The schemafy_core crate contains some bare \r. 😞

$ hexyl schemafy_core-0.6.0/src/lib.rs 
┌────────┬─────────────────────────┬─────────────────────────┬────────┬────────┐
│00000000│ 70 75 62 20 6d 6f 64 20 ┊ 6f 6e 65 5f 6f 72 5f 6d │pub mod ┊one_or_m│
│00000010│ 61 6e 79 3b 0d 0d 0a    ┊                         │any;___ ┊        │
└────────┴─────────────────────────┴─────────────────────────┴────────┴────────┘

Notice the file ends with \r\r\n.