Remove unused certificate files

Lib/test/ssl_cert.pem

------BEGIN CERTIFICATE-----
-MIICLDCCAdYCAQAwDQYJKoZIhvcNAQEEBQAwgaAxCzAJBgNVBAYTAlBUMRMwEQYD
-VQQIEwpRdWVlbnNsYW5kMQ8wDQYDVQQHEwZMaXNib2ExFzAVBgNVBAoTDk5ldXJv
-bmlvLCBMZGEuMRgwFgYDVQQLEw9EZXNlbnZvbHZpbWVudG8xGzAZBgNVBAMTEmJy
-dXR1cy5uZXVyb25pby5wdDEbMBkGCSqGSIb3DQEJARYMc2FtcG9AaWtpLmZpMB4X
-DTk2MDkwNTAzNDI0M1oXDTk2MTAwNTAzNDI0M1owgaAxCzAJBgNVBAYTAlBUMRMw
-EQYDVQQIEwpRdWVlbnNsYW5kMQ8wDQYDVQQHEwZMaXNib2ExFzAVBgNVBAoTDk5l
-dXJvbmlvLCBMZGEuMRgwFgYDVQQLEw9EZXNlbnZvbHZpbWVudG8xGzAZBgNVBAMT
-EmJydXR1cy5uZXVyb25pby5wdDEbMBkGCSqGSIb3DQEJARYMc2FtcG9AaWtpLmZp
-MFwwDQYJKoZIhvcNAQEBBQADSwAwSAJBAL7+aty3S1iBA/+yxjxv4q1MUTd1kjNw
-L4lYKbpzzlmC5beaQXeQ2RmGMTXU+mDvuqItjVHOK3DvPK7lTcSGftUCAwEAATAN
-BgkqhkiG9w0BAQQFAANBAFqPEKFjk6T6CKTHvaQeEAsX0/8YHPHqH/9AnhSjrwuX
-9EBc0n6bVGhN7XaXd6sJ7dym9sbsWxb+pJdurnkxjx4=
------END CERTIFICATE-----

Lib/test/ssl_key.pem

------BEGIN RSA PRIVATE KEY-----
-MIIBPAIBAAJBAL7+aty3S1iBA/+yxjxv4q1MUTd1kjNwL4lYKbpzzlmC5beaQXeQ
-2RmGMTXU+mDvuqItjVHOK3DvPK7lTcSGftUCAwEAAQJBALjkK+jc2+iihI98riEF
-oudmkNziSRTYjnwjx8mCoAjPWviB3c742eO3FG4/soi1jD9A5alihEOXfUzloenr
-8IECIQD3B5+0l+68BA/6d76iUNqAAV8djGTzvxnCxycnxPQydQIhAMXt4trUI3nc
-a+U8YL2HPFA3gmhBsSICbq2OptOCnM7hAiEA6Xi3JIQECob8YwkRj29DU3/4WYD7
-WLPgsQpwo1GuSpECICGsnWH5oaeD9t9jbFoSfhJvv0IZmxdcLpRcpslpeWBBAiEA
-6/5B8J0GHdJq89FHwEG/H2eVVUYu5y/aD6sgcm+0Avg=
------END RSA PRIVATE KEY-----