Update SSL_CTX_set0_buffer_pool reflecting CRYPTO_BUFFER_POOL changes

After https://boringssl-review.googlesource.com/c/boringssl/+/90154, the
rules are more lax, but ones does still need to be aware of SSL_CTX vs
SSL lifetimes.

Change-Id: I20b7516f99ab1f896ae0b46411cd284eea4546a2
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/92987
Commit-Queue: Xiangfei Ding <xfding@google.com>
Auto-Submit: David Benjamin <davidben@google.com>
Presubmit-BoringSSL-Verified: boringssl-scoped@luci-project-accounts.iam.gserviceaccount.com <boringssl-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Xiangfei Ding <xfding@google.com>
diff --git a/include/openssl/ssl.h b/include/openssl/ssl.h
index e3421f0..3a2e6dc 100644
--- a/include/openssl/ssl.h
+++ b/include/openssl/ssl.h
@@ -734,9 +734,12 @@
 // store certificates. This can allow multiple connections to share
 // certificates and thus save memory.
 //
-// The SSL_CTX does not take ownership of |pool| and the caller must ensure
-// that |pool| outlives |ctx| and all objects linked to it, including |SSL|,
-// |X509| and |SSL_SESSION| objects. Basically, don't ever free |pool|.
+// |ctx| does not take ownership of |pool|. The caller must ensure that |pool|
+// outlives |ctx|, as well as any |SSL| objects referencing |ctx|. (|SSL|
+// objects will increment an |SSL_CTX|'s reference count.) It is not necessary
+// for |pool| to outlive any |CRYPTO_BUFFER|s derived from it, so there is no
+// lifetime constraint on |X509| or |SSL_SESSION| objects created from the
+// connection.
 OPENSSL_EXPORT void SSL_CTX_set0_buffer_pool(SSL_CTX *ctx,
                                              CRYPTO_BUFFER_POOL *pool);