Clarify X509_STORE_CTX_init() documentation in the man page

Fixes #21203
CLA: trivial

Reviewed-by: Todd Short <todd.short@me.com>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from #23435)

(cherry picked from commit 22f82d4)

doc/man3/X509_STORE_CTX_new.pod

@@ -83,7 +83,9 @@ is no longer valid.
 If I<ctx> is NULL nothing is done.
 
 X509_STORE_CTX_init() sets up I<ctx> for a subsequent verification operation.
-It must be called before each call to L<X509_verify_cert(3)> or
+
+X509_STORE_CTX_init() initializes the internal state and resources of the
+X509_STORE_CTX, and must be called before each call to L<X509_verify_cert(3)> or
 L<X509_STORE_CTX_verify(3)>, i.e., a context is only good for one verification.
 If you want to verify a further certificate or chain with the same I<ctx>
 then you must call X509_STORE_CTX_init() again.