Convert ecdsa_p224_key.pem to PKCS#8.

That file was added later, so it wasn't covered by
https://boringssl-review.googlesource.com/9020. Other stacks find PKCS#8 easier
to parse and it's all the same to us.

Change-Id: I56d721a3f33209944cd939552f610041344bbbcd
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/36164
Reviewed-by: Adam Langley <agl@google.com>

ssl/test/runner/ecdsa_p224_key.pem

diff --git a/ssl/test/runner/ecdsa_p224_key.pem b/ssl/test/runner/ecdsa_p224_key.pem
index cfe411b..d62594b 100644
--- a/ssl/test/runner/ecdsa_p224_key.pem
+++ b/ssl/test/runner/ecdsa_p224_key.pem
@@ -1,5 +1,5 @@
------BEGIN EC PRIVATE KEY-----
-MGgCAQEEHGi+rNLi+gHJqmRRtdlLBOw1WYv7H/VnlYGAZ0+gBwYFK4EEACGhPAM6
-AATp26Xp0vT4LKigWIorhX4Rg1g9sxmgtPFFyNGCvDd1vpDMEC+INLEoANNW7JGZ
-pULvgx/pugEcOQ==
------END EC PRIVATE KEY-----
+-----BEGIN PRIVATE KEY-----
+MHgCAQAwEAYHKoZIzj0CAQYFK4EEACEEYTBfAgEBBBxovqzS4voByapkUbXZSwTs
+NVmL+x/1Z5WBgGdPoTwDOgAE6dul6dL0+CyooFiKK4V+EYNYPbMZoLTxRcjRgrw3
+db6QzBAviDSxKADTVuyRmaVC74Mf6boBHDk=
+-----END PRIVATE KEY-----