Update strum requirement from 0.26 to 0.27 (#113)

Author: dependabot[bot]

swiftnav/Cargo.toml

@@ -13,7 +13,7 @@ rust-version = "1.62.1"
 rustversion = "1.0"
 chrono = { version = "0.4", optional = true }
 swiftnav-sys = { version = "^0.10.0", path = "../swiftnav-sys/" }
-strum = { version = "0.26", features = ["derive"] }
+strum = { version = "0.27", features = ["derive"] }
 
 [dev-dependencies]
 float_eq = "1.0.1"