jtreg-wrappers: Limit BC test variants to linux and windows

[zzambers]

Even with sed fix, there is still some other problem (exception) on MacOS in BC (BouncyCastle) variant:

Error: Exception in thread "main" java.io.IOException: keystore password was incorrect
	at java.base/sun.security.pkcs12.PKCS12KeyStore.engineLoad(PKCS12KeyStore.java:2116)
	at java.base/sun.security.util.KeyStoreDelegator.engineLoad(KeyStoreDelegator.java:222)
	at java.base/java.security.KeyStore.load(KeyStore.java:1479)
	at SSLSocketTester.loadKeystore(SSLSocketTester.java:148)
	at SSLSocketTester.getKeyManagers(SSLSocketTester.java:123)
	at SSLSocketTester.init(SSLSocketTester.java:94)
	at Main.main(Main.java:29)
Caused by: java.security.UnrecoverableKeyException: failed to decrypt safe contents entry: javax.crypto.BadPaddingException: Given final block not properly padded. Such issues can arise if a bad key is used during decryption.
	... 7 more

As debugging problems with only GHA, without access to physical machine, is clumsy and time consuming, I am not going to dig into it right now and rather limit jtreg-wrappers to run BC variants only on Linux and Windows. Jtreg-wrappers still run ssl-tests in basic configuration on MacOS.