crypto/tls,regexp: remove always-nil error results

These were harmless, but added unnecessary verbosity to the code.
This can happen as a result of refactors: for example,
the method sessionState used to return errors in some cases.

Change-Id: I4e6dacc01ae6a49b528c672979f95cbb86795a85
Reviewed-on: https://go-review.googlesource.com/c/go/+/528995
Reviewed-by: Leo Isla <islaleo93@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Olivier Mengué <olivier.mengue@gmail.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: qiulaidongfeng <2645477756@qq.com>
Reviewed-by: Quim Muntal <quimmuntal@gmail.com>

handshake_server.go

@@ -802,10 +802,7 @@ func (hs *serverHandshakeState) sendSessionTicket() error {
 	c := hs.c
 	m := new(newSessionTicketMsg)
 
-	state, err := c.sessionState()
-	if err != nil {
-		return err
-	}
+	state := c.sessionState()
 	state.secret = hs.masterSecret
 	if hs.sessionState != nil {
 		// If this is re-wrapping an old key, then keep
@@ -813,6 +810,7 @@ func (hs *serverHandshakeState) sendSessionTicket() error {
 		state.createdAt = hs.sessionState.createdAt
 	}
 	if c.config.WrapSession != nil {
+		var err error
 		m.ticket, err = c.config.WrapSession(c.connectionStateLocked(), state)
 		if err != nil {
 			return err