Bump serial_test to 2

Author: djc

Cargo.toml

@@ -17,7 +17,7 @@ rustls-pemfile = "1"
 ring = "0.16.5"
 rustls = "0.21.0"
 rustls-webpki = "0.100"
-serial_test = "0.8" # later versions depend on dashmap, which requires a newer MSRV
+serial_test = "2"
 untrusted = "0.7.0" # stick to the version ring depends on for now
 webpki-roots = "0.23"
 x509-parser = "0.15"