fix(test): exclude more File-based test cases from miri

Miri sometimes non-deterministically has its mocks for read(2)/write(2)
do only partial reads/writes, which our unittests cannot deal with. See
also commit 029c652 ("fix(test): do not try to read files under
miri"). Mark these test cases as cfg(not(miri)).

Signed-off-by: Patrick Roy <roypat@amazon.co.uk>

Author: roypat

src/mmap/mod.rs

@@ -455,6 +455,7 @@ mod tests {
 
     #[test]
     #[cfg(feature = "rawfd")]
+    #[cfg(not(miri))]
     fn read_to_and_write_from_mem() {
         use std::mem;