test_asn1.rb: Remove the assertions of the time string format without second.

[ This is a backport to the 3.0 branch. ]

This commit fixes the following errors in the tests.
Because the OpenSSL project changed the code to make the time string format
without second invalid. So, we drop the assertions.

```
1) Error: test_generalizedtime(OpenSSL::TestASN1): OpenSSL::ASN1::ASN1Error: generalizedtime is too short
/home/runner/work/ruby-openssl/ruby-openssl/test/openssl/test_asn1.rb:698:in `decode'
/home/runner/work/ruby-openssl/ruby-openssl/test/openssl/test_asn1.rb:698:in `decode_test'
/home/runner/work/ruby-openssl/ruby-openssl/test/openssl/test_asn1.rb:433:in `test_generalizedtime'
     430:       OpenSSL::ASN1::GeneralizedTime.new(Time.utc(9999, 9, 8, 23, 43, 39))
     431:     # LibreSSL 3.6.0 requires the seconds element
     432:     return if libressl?
  => 433:     decode_test B(%w{ 18 0D }) + "201612081934Z".b,
     434:       OpenSSL::ASN1::GeneralizedTime.new(Time.utc(2016, 12, 8, 19, 34, 0))
     435:     # not implemented
     436:     # decode_test B(%w{ 18 13 }) + "20161208193439+0930".b,

2) Error: test_utctime(OpenSSL::TestASN1): OpenSSL::ASN1::ASN1Error: utctime is too short
/home/runner/work/ruby-openssl/ruby-openssl/test/openssl/test_asn1.rb:698:in `decode'
/home/runner/work/ruby-openssl/ruby-openssl/test/openssl/test_asn1.rb:698:in `decode_test'
/home/runner/work/ruby-openssl/ruby-openssl/test/openssl/test_asn1.rb:411:in `test_utctime'
     408:     end
     409:     # Seconds is omitted. LibreSSL 3.6.0 requires it
     410:     return if libressl?
  => 411:     decode_test B(%w{ 17 0B }) + "1609082343Z".b,
     412:       OpenSSL::ASN1::UTCTime.new(Time.utc(2016, 9, 8, 23, 43, 0))
     413:     # not implemented
     414:     # decode_test B(%w{ 17 11 }) + "500908234339+0930".b,
```

(cherry picked from commit 2e826d5)

Author: junaruga

test/openssl/test_asn1.rb

@@ -411,10 +411,6 @@ def test_utctime
     rescue OpenSSL::ASN1::ASN1Error
       pend "No negative time_t support?"
     end
-    # Seconds is omitted. LibreSSL 3.6.0 requires it
-    return if libressl?
-    decode_test B(%w{ 17 0B }) + "1609082343Z".b,
-      OpenSSL::ASN1::UTCTime.new(Time.utc(2016, 9, 8, 23, 43, 0))
     # not implemented
     # decode_test B(%w{ 17 11 }) + "500908234339+0930".b,
     #   OpenSSL::ASN1::UTCTime.new(Time.new(1950, 9, 8, 23, 43, 39, "+09:30"))
@@ -433,10 +429,6 @@ def test_generalizedtime
       OpenSSL::ASN1::GeneralizedTime.new(Time.utc(2016, 12, 8, 19, 34, 29))
     encode_decode_test B(%w{ 18 0F }) + "99990908234339Z".b,
       OpenSSL::ASN1::GeneralizedTime.new(Time.utc(9999, 9, 8, 23, 43, 39))
-    # LibreSSL 3.6.0 requires the seconds element
-    return if libressl?
-    decode_test B(%w{ 18 0D }) + "201612081934Z".b,
-      OpenSSL::ASN1::GeneralizedTime.new(Time.utc(2016, 12, 8, 19, 34, 0))
     # not implemented
     # decode_test B(%w{ 18 13 }) + "20161208193439+0930".b,
     #   OpenSSL::ASN1::GeneralizedTime.new(Time.new(2016, 12, 8, 19, 34, 39, "+09:30"))