Remove ram_storage feature

We don't need to build a production key without persistent storage. Tests and
fuzzing continue to use the std feature to use the RAM implementation (that does
sanity checks).

Cargo.toml

@@ -25,7 +25,6 @@ debug_allocations = ["lang_items/debug_allocations"]
 debug_ctap = ["crypto/derive_debug", "libtock_drivers/debug_ctap"]
 panic_console = ["lang_items/panic_console"]
 std = ["cbor/std", "crypto/std", "crypto/derive_debug", "lang_items/std", "persistent_store/std"]
-ram_storage = []
 verbose = ["debug_ctap", "libtock_drivers/verbose_usb"]
 with_ctap1 = ["crypto/with_ctap1"]
 with_ctap2_1 = []