qt: Revert "Force TLS1.0+ for SSL connections"
qt: Revert "Force TLS1.0+ for SSL connections"

This reverts commit 15e26a6a9afe299b9ca6fced73b876644365879b, whose
purpose was to tweak the Qt configuration to force TLS, i.e., to
disable SSLv3, in Qt versions >= 5.5. However, the default behavior
of Qt >= 5.4 is to disable SSLv3 anyway [1], so the configuration
tweak is redundant.

With Qt 5.11.2, the configuration tweak is not only redundant but in
fact provokes a deadlock (#14359) due to Qt 5.11.2 being incompatible
with OpenSSL 1.1.1 [2]. Since the deadlock occurs at the early startup
stage of bitcoin-qt, it renders bitcoin-qt entirely non-functional
when compiled against OpenSSL 1.1.1 and Qt 5.11.2 (and possible future
combinations of OpenSSL and Qt versions).

This commit fixes #14359 by removing the redundant code.

[1] https://code.qt.io/cgit/qt/qtbase.git/commit/?id=3fd2d9eff8c1f948306ee5fbfe364ccded1c4b84
[2] https://bugreports.qt.io/browse/QTBUG-70956

Github-Pull: #14403
Rebased-From: 7d173c4cd1885ff5bcf9e5f8f7f712138dd8a445
Tree-SHA512: 71a34b13202c834c5ca73bcb9b70efff26c34e1aac3b954f098620b62c2be53a8e319929c4764a5b5cc5d0dd163ff70f4eb3a4f1f608363b7d23d1b16b25ddc7

BTCGPU/BTCGPU,qtumproject/qtum,GroestlCoin/GroestlCoin,digibyte/digibyte,thrasher-/litecoin,vertcoin/vertcoin,digibyte/digibyte,digibyte/digibyte,GroestlCoin/GroestlCoin,vmp32k/litecoin,GroestlCoin/GroestlCoin,BTCGPU/BTCGPU,GroestlCoin/bitcoin,thrasher-/litecoin,vmp32k/litecoin,ahmedbodi/vertcoin,BTCGPU/BTCGPU,h4x3rotab/BTCGPU,lbryio/lbrycrd,vmp32k/litecoin,qtumproject/qtum,GroestlCoin/GroestlCoin,ahmedbodi/vertcoin,gjhiggins/vcoincore,GroestlCoin/GroestlCoin,lbryio/lbrycrd,qtumproject/qtum,guncoin/guncoin,vmp32k/litecoin,qtumproject/qtum,gjhiggins/vcoincore,guncoin/guncoin,guncoin/guncoin,ahmedbodi/vertcoin,gjhiggins/vcoincore,gjhiggins/vcoincore,h4x3rotab/BTCGPU,qtumproject/qtum,BTCGPU/BTCGPU,thrasher-/litecoin,vertcoin/vertcoin,ahmedbodi/vertcoin,lbryio/lbrycrd,BTCGPU/BTCGPU,qtumproject/qtum,vmp32k/litecoin,GroestlCoin/bitcoin,gjhiggins/vcoincore,lbryio/lbrycrd,lbryio/lbrycrd,thrasher-/litecoin,h4x3rotab/BTCGPU,lbryio/lbrycrd,qtumproject/qtum,BTCGPU/BTCGPU,GroestlCoin/bitcoin,GroestlCoin/GroestlCoin,ahmedbodi/vertcoin,ahmedbodi/vertcoin,GroestlCoin/bitcoin,guncoin/guncoin,guncoin/guncoin,digibyte/digibyte,thrasher-/litecoin,vertcoin/vertcoin,h4x3rotab/BTCGPU,h4x3rotab/BTCGPU,guncoin/guncoin,vertcoin/vertcoin,gjhiggins/vcoincore,lbryio/lbrycrd,h4x3rotab/BTCGPU,thrasher-/litecoin,vmp32k/litecoin,vertcoin/vertcoin,vertcoin/vertcoin,digibyte/digibyte,GroestlCoin/bitcoin,GroestlCoin/bitcoin,digibyte/digibyte