deprecate auto-idna on UniformResourceIdentifier (#3832)

* deprecate auto-idna on UniformResourceIdentifier

* fix repr test

* docs

* some updated language
diff --git a/tests/test_x509.py b/tests/test_x509.py
index 661461d..58d3e54 100644
--- a/tests/test_x509.py
+++ b/tests/test_x509.py
@@ -229,7 +229,7 @@
             )
         ])
         assert ian.value == x509.IssuerAlternativeName([
-            x509.UniformResourceIdentifier(u"https://cryptography.io"),
+            x509.UniformResourceIdentifier(b"https://cryptography.io"),
         ])
 
     def test_signature(self, backend):
@@ -1506,7 +1506,7 @@
         aia = x509.AuthorityInformationAccess([
             x509.AccessDescription(
                 x509.ObjectIdentifier("2.999.7"),
-                x509.UniformResourceIdentifier(u"http://example.com")
+                x509.UniformResourceIdentifier(b"http://example.com")
             ),
         ])
 
@@ -3154,11 +3154,11 @@
         aia = x509.AuthorityInformationAccess([
             x509.AccessDescription(
                 AuthorityInformationAccessOID.OCSP,
-                x509.UniformResourceIdentifier(u"http://ocsp.domain.com")
+                x509.UniformResourceIdentifier(b"http://ocsp.domain.com")
             ),
             x509.AccessDescription(
                 AuthorityInformationAccessOID.CA_ISSUERS,
-                x509.UniformResourceIdentifier(u"http://domain.com/ca.crt")
+                x509.UniformResourceIdentifier(b"http://domain.com/ca.crt")
             )
         ])