doc: update documentation to note removal of ERR_GET_FUNC()

Reviewed-by: Nicola Tuveri <nic.tuv@gmail.com>
(Merged from https://github.com/openssl/openssl/pull/16004)

doc/man3/ERR_GET_LIB.pod

@@ -2,7 +2,7 @@
 
 =head1 NAME
 
-ERR_GET_LIB, ERR_GET_FUNC, ERR_GET_REASON, ERR_FATAL_ERROR
+ERR_GET_LIB, ERR_GET_REASON, ERR_FATAL_ERROR
 - get information from error codes
 
 =head1 SYNOPSIS
@@ -11,8 +11,6 @@ ERR_GET_LIB, ERR_GET_FUNC, ERR_GET_REASON, ERR_FATAL_ERROR
 
  int ERR_GET_LIB(unsigned long e);
 
- int ERR_GET_FUNC(unsigned long e);
-
  int ERR_GET_REASON(unsigned long e);
 
  int ERR_FATAL_ERROR(unsigned long e);
@@ -20,7 +18,7 @@ ERR_GET_LIB, ERR_GET_FUNC, ERR_GET_REASON, ERR_FATAL_ERROR
 =head1 DESCRIPTION
 
 The error code returned by ERR_get_error() consists of a library
-number, function code and reason code. ERR_GET_LIB(), ERR_GET_FUNC()
+number, function code and reason code. ERR_GET_LIB()
 and ERR_GET_REASON() can be used to extract these.
 
 ERR_FATAL_ERROR() indicates whether a given error code is a fatal error.
@@ -37,8 +35,7 @@ B<ERR_R_...> reason codes such as B<ERR_R_MALLOC_FAILURE> are globally
 unique. However, when checking for sub-library specific reason codes,
 be sure to also compare the library number.
 
-ERR_GET_LIB(), ERR_GET_FUNC(), ERR_GET_REASON(), and ERR_FATAL_ERROR()
-are macros.
+ERR_GET_LIB(), ERR_GET_REASON(), and ERR_FATAL_ERROR() are macros.
 
 =head1 RETURN VALUES
 
@@ -52,8 +49,9 @@ L<ERR_get_error(3)>
 
 =head1 HISTORY
 
-ERR_GET_LIB(), ERR_GET_FUNC() and ERR_GET_REASON() are available in
-all versions of OpenSSL.
+ERR_GET_LIB() and ERR_GET_REASON() are available in all versions of OpenSSL.
+
+ERR_GET_FUNC() was removed in OpenSSL 3.0.
 
 =head1 COPYRIGHT