rust: Fix cargo clippy and cargo doc findings

Fix the new `cargo clippy` and `cargo doc` findings that were triggered
with the recent policy addition.

Signed-off-by: Marc Hartmayer <mhartmay@linux.ibm.com>
Reviewed-by: Steffen Eiden <seiden@linux.ibm.com>
Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>

rust/pv/src/openssl_extensions/crl.rs

@@ -77,7 +77,7 @@ impl X509StoreContextExtension for X509StoreContextRef {
     {
         struct Cleanup<'a>(&'a mut X509StoreContextRef);
 
-        impl<'a> Drop for Cleanup<'a> {
+        impl Drop for Cleanup<'_> {
             fn drop(&mut self) {
                 unsafe {
                     openssl_sys::X509_STORE_CTX_cleanup(self.0.as_ptr());

rust/pv/src/openssl_extensions/stackable_crl.rs

@@ -63,7 +63,7 @@ impl Stackable for StackableX509Crl {
 }
 
 pub struct MemBioSlice<'a>(*mut openssl_sys::BIO, PhantomData<&'a [u8]>);
-impl<'a> Drop for MemBioSlice<'a> {
+impl Drop for MemBioSlice<'_> {
     fn drop(&mut self) {
         unsafe {
             openssl_sys::BIO_free_all(self.0);