fix use std::mem related lint

Signed-off-by: Jason Volk <jason@zemos.net>

src/service/rooms/pdu_metadata/data.rs

-use std::{mem, sync::Arc};
+use std::{mem::size_of, sync::Arc};
 
 use ruma::{EventId, RoomId, UserId};
 
@@ -44,7 +44,7 @@ fn relations_until<'a>(
 				.iter_from(&current, true)
 				.take_while(move |(k, _)| k.starts_with(&prefix))
 				.map(move |(tofrom, _data)| {
-					let from = utils::u64_from_bytes(&tofrom[(mem::size_of::<u64>())..])
+					let from = utils::u64_from_bytes(&tofrom[(size_of::<u64>())..])
 						.map_err(|_| Error::bad_database("Invalid count in tofrom_relation."))?;
 
 					let mut pduid = shortroomid.to_be_bytes().to_vec();

src/service/rooms/read_receipt/data.rs

-use std::mem;
+use std::mem::size_of;
 
 use ruma::{
 	events::{receipt::ReceiptEvent, AnySyncEphemeralRoomEvent},
@@ -86,10 +86,10 @@ fn readreceipts_since<'a>(
 				.iter_from(&first_possible_edu, false)
 				.take_while(move |(k, _)| k.starts_with(&prefix2))
 				.map(move |(k, v)| {
-					let count = utils::u64_from_bytes(&k[prefix.len()..prefix.len() + mem::size_of::<u64>()])
+					let count = utils::u64_from_bytes(&k[prefix.len()..prefix.len() + size_of::<u64>()])
 						.map_err(|_| Error::bad_database("Invalid readreceiptid count in db."))?;
 					let user_id = UserId::parse(
-						utils::string_from_bytes(&k[prefix.len() + mem::size_of::<u64>() + 1..])
+						utils::string_from_bytes(&k[prefix.len() + size_of::<u64>() + 1..])
 							.map_err(|_| Error::bad_database("Invalid readreceiptid userid bytes in db."))?,
 					)
 					.map_err(|_| Error::bad_database("Invalid readreceiptid userid in db."))?;

src/service/rooms/threads/data.rs

-use std::mem;
+use std::mem::size_of;
 
 use ruma::{api::client::threads::get_threads::v1::IncludeThreads, OwnedUserId, RoomId, UserId};
 
@@ -35,7 +35,7 @@ fn threads_until<'a>(
 				.iter_from(&current, true)
 				.take_while(move |(k, _)| k.starts_with(&prefix))
 				.map(move |(pduid, _users)| {
-					let count = utils::u64_from_bytes(&pduid[(mem::size_of::<u64>())..])
+					let count = utils::u64_from_bytes(&pduid[(size_of::<u64>())..])
 						.map_err(|_| Error::bad_database("Invalid pduid in threadid_userids."))?;
 					let mut pdu = services()
 						.rooms