tests: rename better_tls test to path_building

The `better_tls` unit test in the `better_tls.rs` integration test
module was named before we added the `name_constraints` unit test. This
commit renames the `better_tls` unit test to `path_building` to reflect
that it runs the path building testsuite from bettertls.

Author: cpu

tests/better_tls.rs

@@ -14,7 +14,7 @@ use webpki::{extract_trust_anchor, KeyUsage, SubjectNameRef};
 
 #[ignore] // Runs slower than other unit tests - opt-in with `cargo test -- --ignored`
 #[test]
-fn better_tls() {
+fn path_building() {
     let better_tls = testdata();
     let root_der = &better_tls.root_der();
     let root_der = CertificateDer::from(root_der.as_slice());