rhi: gl: Correctly report WideLines for OpenGL

In core profile contexts a line width other than 1 may not work
as expected since it is deprecated in the core profile.

Change-Id: I3fc33cf90c65156aa87d04f08518c9ddcfb62625
Reviewed-by: Andy Nichols <andy.nichols@qt.io>

src/gui/rhi/qrhi.cpp

@@ -544,7 +544,8 @@ Q_LOGGING_CATEGORY(QRHI_LOG_INFO, "qt.rhi.general")
     supported. When reported as not supported, the line width set on the
     graphics pipeline state is ignored. This can always be false with some
     backends (D3D11, Metal). With Vulkan, the value depends on the
-    implementation.
+    implementation. With OpenGL, wide lines are not supported in core profile
+    contexts.
 
     \value VertexShaderPointSize Indicates that the size of rasterized points
     set via \c{gl_PointSize} in the vertex shader is taken into account. When

src/gui/rhi/qrhigles2.cpp

@@ -887,7 +887,7 @@ bool QRhiGles2::isFeatureSupported(QRhi::Feature feature) const
     case QRhi::Compute:
         return caps.compute;
     case QRhi::WideLines:
-        return true;
+        return !caps.coreProfile;
     case QRhi::VertexShaderPointSize:
         return true;
     case QRhi::BaseVertex: