GL: fix "firefox-fake-disjoint-timer-query-webgl2" detection.

Firefox used to report iself as "Mozilla by Mozilla" but it's now
"Something whatever by Mozilla" which broke the detection.

doc/changelog.dox

@@ -970,6 +970,10 @@ See also:
     [mosra/magnum#535](https://github.com/mosra/magnum/issues/535))
 -   Fixed various wrong assumptions about Mac builds being always desktop GLES
     (see [mosra/magnum#](https://github.com/mosra/magnum/issues/541))
+-   Fixed the @cpp "firefox-fake-disjoint-timer-query-webgl2" @ce workaround to
+    work on Firefox again. The reported renderer string got changed, possibly
+    in relation to @webgl_extension{WEBGL,debug_renderer_info} being
+    deprecated, which broke Firefox detection in the workaround enabling code.
 
 @subsection changelog-latest-deprecated Deprecated APIs
 

src/Magnum/GL/Implementation/driverSpecific.cpp

@@ -743,7 +743,12 @@ void Context::setupDriverWorkarounds() {
     #endif
 
     #if defined(MAGNUM_TARGET_WEBGL) && !defined(MAGNUM_TARGET_GLES2)
-    if(rendererString() == "Mozilla"_s) {
+    /* Firefox used to report both rendererString() and vendorString() as
+       Mozilla (printing silly `Renderer: Mozilla by Mozilla` in the Magnum
+       startup log), but possibly in relation with WEBGL_debug_renderer_info
+       being deprecated in FF 92+ this changed and now Mozilla is only in
+       vendorString() and rendererString() is the actual system GPU. */
+    if(vendorString() == "Mozilla"_s) {
         for(const auto& extension: extensionStrings()) {
             if(extension == "GL_EXT_disjoint_timer_query"_s && !isDriverWorkaroundDisabled("firefox-fake-disjoint-timer-query-webgl2"_s)) {
                 _extensionStatus.set(Extensions::EXT::disjoint_timer_query_webgl2::Index, true);