build(meson): mark *_encrypted_pem as test deps (#1255)

Meson only runs required targets. The key_encrypted_pem and
cert_encrypted_pem targets added in 020b0db090
and 8191fd8e6c weren't added to the list
of targets required by the test target, so the generation of the
encrypted certs was skipped, resulting in the failure of
BindServerTest.BindAndListenSeparatelySSLEncryptedKey.

test/meson.build

@@ -100,6 +100,8 @@ test(
     key_pem,
     cert_pem,
     cert2_pem,
+    key_encrypted_pem,
+    cert_encrypted_pem,
     rootca_key_pem,
     rootca_cert_pem,
     client_key_pem,