Reference specific MSRV in comment

This will make it easier to remove the now-unneeded `unsafe` when we
update MSRV.

Author: joshtriplett

src/wasi.rs

@@ -366,7 +366,7 @@ pub const _SC_PAGE_SIZE: ::c_int = _SC_PAGESIZE;
 pub const _SC_IOV_MAX: c_int = 60;
 pub const _SC_SYMLOOP_MAX: c_int = 173;
 
-#[allow(unused_unsafe)] // `addr_of!(EXTERN_STATIC)` is now considered safe
+#[allow(unused_unsafe)] // `addr_of!(EXTERN_STATIC)` is now safe; remove `unsafe` when MSRV >= 1.82
 pub static CLOCK_MONOTONIC: clockid_t = unsafe { clockid_t(ptr_addr_of!(_CLOCK_MONOTONIC)) };
 #[allow(unused_unsafe)]
 pub static CLOCK_PROCESS_CPUTIME_ID: clockid_t =