remove dead code related to deprecated Android versions

app/src/main/java/de/blinkt/openvpn/VpnProfile.java

app/src/main/java/de/blinkt/openvpn/core/NativeUtils.java

app/src/main/java/de/blinkt/openvpn/core/NetworkSpace.java

app/src/main/java/de/blinkt/openvpn/core/NetworkUtils.java

app/src/main/java/de/blinkt/openvpn/core/OpenVPNService.java

.../java/de/blinkt/openvpn/core/OpenVpnManagementThread.java

...src/main/java/de/blinkt/openvpn/core/VPNLaunchHelper.java

...e/leap/bitmaskclient/base/fragments/SettingsFragment.java

...ain/java/se/leap/bitmaskclient/base/utils/ViewHelper.java

...c/main/java/se/leap/bitmaskclient/eip/VoidVpnService.java

...nt/providersetup/activities/ConfigWizardBaseActivity.java