the great persy, sled, and heed purge (and bump MSRV to 1.74.1)

these database backends are either unmaintained, broken in conduit, or
incredibly niche for something like conduwuit.

also i want to bump the MSRV.

Signed-off-by: strawberry <strawberry@puppygock.gay>

docker/README.md

@@ -64,7 +64,7 @@ docker run -d -p 8448:6167 \
   -e CONDUIT_MAX_REQUEST_SIZE="20_000_000" \
   -e CONDUIT_TRUSTED_SERVERS="[\"matrix.org\"]" \
   -e CONDUIT_MAX_CONCURRENT_REQUESTS="100" \
-  -e CONDUIT_LOG="warn,rocket=off,_=off,sled=off" \
+  -e CONDUIT_LOG="warn,state_res=warn" \
   --name conduit <link>
 ```