WebView::LogMessageSecurityLevel cast is broken

The log level transmitted through Oxide isn't strongly typed, and it's cast to LogMessageSecurityLevel in OxideQQuickWebView. At some point, the logging levels have changed which breaks this cast.

The cast currently works like this:

 -1 (logging::LOG_VERBOSE) -> LogSeverityVerbose
 0 (logging::LOG_INFO) -> LogSeverityInfo
 1 (logging::LOG_WARNING) -> LogSeverityWarning
 2 (logging::LOG_ERROR) -> LogSeverityError
 3 (logging::LOG_FATAL) -> LogSeverityErrorReport

No valid logging level casts to LogSeverityFatal.

This cast is unsafe anyway - we should only ever be casting like this if we have appropriate static_asserts to catch breakage like this.

Obviously, LogSeverityErrorReport is obsolete and unused. But it turns out that LogSeverityFatal is unused too (blink can't log fatal errors - those are a result of DCHECKs).