Compiler Attributes: remove comment about sparse not supporting __has_attribute

Sparse supports __has_attribute() since 2018-08-31, so the comment
is not true anymore but more importantly is rather confusing.

So remove it.
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>

include/linux/compiler_attributes.h

@@ -24,12 +24,6 @@
  * __has_attribute is supported on gcc >= 5, clang >= 2.9 and icc >= 17.
  * In the meantime, to support 4.6 <= gcc < 5, we implement __has_attribute
  * by hand.
- *
- * sparse does not support __has_attribute (yet) and defines __GNUC_MINOR__
- * depending on the compiler used to build it; however, these attributes have
- * no semantic effects for sparse, so it does not matter. Also note that,
- * in order to avoid sparse's warnings, even the unsupported ones must be
- * defined to 0.
  */
 #ifndef __has_attribute
 # define __has_attribute(x) __GCC4_has_attribute_##x