Fix a doc-nits failure

We need blank lines on each side of a section heading.

Reviewed-by: Matthias St. Pierre <Matthias.St.Pierre@ncp-e.com>
(Merged from https://github.com/openssl/openssl/pull/9192)

doc/internal/man3/ossl_init_thread_deregister.pod

@@ -1,10 +1,12 @@
 =pod
 
 =head1 NAME
+
 OSSL_thread_stop_handler_fn,
 ossl_init_thread_start,
 ossl_init_thread_deregister
 - internal thread routines
+
 =head1 SYNOPSIS
 
  #include "internal/cryptlib_int.h"