tests: Drop openat override

No longer needed.

tests/inst/Cargo.toml

@@ -46,7 +46,3 @@ with-procspawn-tempdir = { git = "https://github.com/cgwalters/with-procspawn-te
 
 # Internal crate for the test macro
 itest-macro = { path = "itest-macro" }
-
-[patch.crates-io]
-# PR openat (pun intended) https://github.com/tailhook/openat/pull/36
-openat = { git = 'https://github.com/cgwalters/openat', branch = 'libc-rename-signed' }