doc: Remove clang-parsing definitions

These definitions were just set to the default (off), but their presence
causes Fedora's Doxygen to emit a warning as it is not compiled with
Clang support.

Remove them as they are no-ops anyway.

Signed-off-by: Daniel Stone <daniels@collabora.com>

doc/sphinx/doxygen.ini.in

@@ -1073,25 +1073,6 @@ USE_HTAGS              = NO
 
 VERBATIM_HEADERS       = YES
 
-# If the CLANG_ASSISTED_PARSING tag is set to YES then doxygen will use the
-# clang parser (see: http://clang.llvm.org/) for more accurate parsing at the
-# cost of reduced performance. This can be particularly helpful with template
-# rich C++ code for which doxygen's built-in parser lacks the necessary type
-# information.
-# Note: The availability of this option depends on whether or not doxygen was
-# generated with the -Duse-libclang=ON option for CMake.
-# The default value is: NO.
-
-CLANG_ASSISTED_PARSING = NO
-
-# If clang assisted parsing is enabled you can provide the compiler with command
-# line options that you would normally use when invoking the compiler. Note that
-# the include paths will already be set by doxygen for the files and directories
-# specified with INPUT and INCLUDE_PATH.
-# This tag requires that the tag CLANG_ASSISTED_PARSING is set to YES.
-
-CLANG_OPTIONS          =
-
 #---------------------------------------------------------------------------
 # Configuration options related to the alphabetical class index
 #---------------------------------------------------------------------------