Fix Clippy warning related to vector initialization

Author: GabrielMajeri

uefi-test-runner/src/main.rs

@@ -115,13 +115,8 @@ fn shutdown(image: uefi::Handle, st: SystemTable<Boot>) -> ! {
     }
 
     // Exit boot services as a proof that it works :)
-    use crate::alloc::vec::Vec;
     let max_mmap_size = st.boot_services().memory_map_size() + 1024;
-    let mut mmap_storage = unsafe {
-        let mut mmap_storage = Vec::with_capacity(max_mmap_size);
-        mmap_storage.set_len(max_mmap_size);
-        mmap_storage.into_boxed_slice()
-    };
+    let mut mmap_storage = vec![0; max_mmap_size].into_boxed_slice();
     let (st, _iter) = st
         .exit_boot_services(image, &mut mmap_storage[..])
         .expect_success("Failed to exit boot services");