Bump MSRV to 1.71

Author: nicoburns

.github/workflows/main.yml

@@ -18,7 +18,7 @@ jobs:
           - nightly
           - beta
           - stable
-          - 1.68.0
+          - 1.71.0
         features:
           - --no-default-features
           -

Cargo.toml

@@ -10,7 +10,7 @@ readme = "README.md"
 keywords = ["css", "syntax", "parser"]
 license = "MPL-2.0"
 edition = "2018"
-rust-version = "1.68"
+rust-version = "1.71"
 
 exclude = ["src/css-parsing-tests/**", "src/big-data-url.css"]