hints: Rephrase documentation to improve grammar

"This thing allows to do something" is not really grammatically correct.
The closest rephrasing would be "allows one to do something" or "allows
the user to do something", but I think the passive voice reads more
naturally here.

Detected by Debian's lintian QA tool.

Signed-off-by: Simon McVittie <[email protected]>

include/SDL3/SDL_hints.h

@@ -595,7 +595,7 @@ extern "C" {
  * A variable that limits what CPU features are available.
  *
  * By default, SDL marks all features the current CPU supports as available.
- * This hint allows to limit these to a subset.
+ * This hint allows the enabled features to be limited to a subset.
  *
  * When the hint is unset, or empty, SDL will enable all detected CPU
  * features.