[gdb/build, c++20] Fix DISABLE_COPY_AND_ASSIGN use in ui_out_emit_type

[gdb/build, c++20] Fix DISABLE_COPY_AND_ASSIGN use in ui_out_emit_type

When building gdb with -std=c++20, I run into:
...
include/ansidecl.h:342:9: error: expected unqualified-id before ‘const’
  342 |   TYPE (const TYPE&) = delete;                  \
      |         ^~~~~
gdb/ui-out.h:412:3: note: in expansion of macro ‘DISABLE_COPY_AND_ASSIGN’
  412 |   DISABLE_COPY_AND_ASSIGN (ui_out_emit_type<Type>);
      |   ^~~~~~~~~~~~~~~~~~~~~~~
...

Fix this by using "DISABLE_COPY_AND_ASSIGN (ui_out_emit_type)".

Tested on x86_64-linux.