Tests: adjusted TODO for alerts not seen after c7a8bdf5af55.

h2_ssl_proxy_cache.t

diff --git a/h2_ssl_proxy_cache.t b/h2_ssl_proxy_cache.t
index 9cc70b8..2a9d605 100644
--- a/h2_ssl_proxy_cache.t
+++ b/h2_ssl_proxy_cache.t
@@ -121,7 +121,8 @@
 # "aio_write" is used to produce "open socket ... left in connection" alerts.
 
 $t->todo_alerts() if $t->read_file('nginx.conf') =~ /aio_write on/
-	and $t->read_file('nginx.conf') =~ /aio threads/ and $^O eq 'linux';
+	and $t->read_file('nginx.conf') =~ /aio threads/ and $^O eq 'linux'
+	and !$t->has_version('1.21.4');
 
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