ci: pin once_cell to 1.20.3 for MSRV

Author: LagginTimes

ci/pin-msrv.sh

@@ -25,3 +25,4 @@ cargo update -p native-tls --precise "0.2.13"
 cargo update -p flate2 --precise "1.0.35"
 cargo update -p bzip2-sys --precise "0.1.12"
 cargo update -p ring --precise "0.17.12"
+cargo update -p once_cell --precise "1.20.3"