Drop special casing for IIS to cover TLS protocol error

[cmb69]

This had been introduced to fix bug 23220[1], although it is not even clear that IIS caused the problem (some comments mention that this happened with Apache).

Anyhow, in hindsight it seems to be a bad idea to brush warnings about improper implementation of the TLS protocol under the carpet; if a server does not properly implement TLS, users should be aware of that, and report that to the respective developers.

[1] https://bugs.php.net/bug.php?id=23220

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The remaining ERR_get_error() != 0 condition is also somehow fishy; it was supposed to be a fix for https://bugs.php.net/bug.php?id=41770, but the OP claimed it wouldn't fix their issue. And even more confusing: that check is in a branch that is only executed if ERR_peek_error() == 0, so the warning appears to be unreachable.

And from the OpenSSL 1.1.1 documentation;

The SSL_ERROR_SYSCALL with errno value of 0 indicates unexpected EOF from the peer. This will be properly reported as SSL_ERROR_SSL with reason code SSL_R_UNEXPECTED_EOF_WHILE_READING in the OpenSSL 3.0 release because it is truly a TLS protocol error to terminate the connection without a SSL_shutdown().