virtio-bindings: Remove unused feature flags

Since we are only generating bindings for 6.15 kernel now, let's remove
the unused feature flags.

Signed-off-by: Jinank Jain <jinankjain@microsoft.com>

Author: jinankjain

virtio-bindings/CHANGELOG.md

@@ -5,6 +5,7 @@
 - Bindings are now once again distributed with the crate, rather than
   generated at build time.
 - Regenerate bindings with Linux 6.15.
+- Remove unused feature flags and build dependencies.
 
 # v0.2.5
 

virtio-bindings/Cargo.toml

@@ -10,9 +10,5 @@ keywords = ["virtio"]
 license = "BSD-3-Clause OR Apache-2.0"
 
 [features]
-# Kernel version features are deprecated and no longer have any effect,
-# as the kernel headers are backwards compatible.
-virtio-v4_14_0 = []
-virtio-v5_0_0 = []
 
 [dependencies]