Revert "can: Make new_unchecked() safe"

This reverts commit b2d00d1 and
31eabd5.

Mark the constructor as unsafe again to prevent UB in safe code that assumes the CAN IDs to contain valid data.
This is in line with functions like `from_utf8_unchecked()` from the std library.

Author: timokroeger

src/can/id.rs

@@ -25,7 +25,7 @@ impl StandardId {
 
     /// Creates a new `StandardId` without checking if it is inside the valid range.
     #[inline]
-    pub const fn new_unchecked(raw: u16) -> Self {
+    pub const unsafe fn new_unchecked(raw: u16) -> Self {
         Self(raw)
     }
 
@@ -61,7 +61,7 @@ impl ExtendedId {
 
     /// Creates a new `ExtendedId` without checking if it is inside the valid range.
     #[inline]
-    pub const fn new_unchecked(raw: u32) -> Self {
+    pub const unsafe fn new_unchecked(raw: u32) -> Self {
         Self(raw)
     }