refactor: remove unused file (#261)

* refactor: remove unused file

the _legacy file will never be used since the library
requires go 1.21+

* lint: remove unnecessary tag

Author: kruskall

transport/tlscommon/versions_default.go

@@ -15,8 +15,6 @@
 // specific language governing permissions and limitations
 // under the License.
 
-//go:build go1.13
-
 package tlscommon
 
 import (