[SYCL][Doc] Fix rendering of bindless images spec (#19545)

Author: AlexeySachkov

sycl/doc/extensions/experimental/sycl_ext_oneapi_bindless_images.asciidoc

@@ -1531,8 +1531,6 @@ construct `ImageHandle` using an `image_descriptor` with member
 `image_type::gather`. Calling `gather_image` on an `ImageHandle` constructed
 with `image_descriptor::num_channels < 4` will result in undefined behavior.
 
-====
-
 === Recognized standard types [[recognized_standard_types]]
 
 For the purposes of this extension, the following are classified as recognized 
@@ -1545,8 +1543,6 @@ standard types.
 
 Any other types are classified as user-defined types.
 
-===
-
 ==== User-defined types
 
 Some examples of a user-defined types may be: