README-ENGINES: fix the link to the provider API README

Signed-off-by: Beat Bolli <dev@drbeat.li>

Reviewed-by: Paul Yang <kaishen.yy@antfin.com>
Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Matthias St. Pierre <Matthias.St.Pierre@ncp-e.com>
(Merged from https://github.com/openssl/openssl/pull/14173)

README-ENGINES.md

@@ -9,7 +9,7 @@ interface for adding alternative implementations of cryptographic
 primitives, most notably for integrating hardware crypto devices.
 
 The ENGINE interface has its limitations and it has been superseeded
-by the [PROVIDER API](README-Provider.md), it is deprecated in OpenSSL
+by the [PROVIDER API](README-PROVIDERS.md), it is deprecated in OpenSSL
 version 3.0. The following documentation is retained as an aid for
 users who need to maintain or support existing ENGINE implementations.
 Support for new hardware devices or new algorithms should be added