[ruby/prism] Fix printf format attribute on ucrt64-mingw gcc 16.3

`__MINGW_PRINTF_FORMAT` is defined in stdio.h.

```
prism/buffer.c: In function 'pm_buffer_append_format':
prism/buffer.c:114:5: warning: function 'pm_buffer_append_format' might be a candidate for 'gnu_printf' format attribute [-Wsuggest-attribute=format]
  114 |     int result = vsnprintf(NULL, 0, format, arguments);
      |     ^~~
prism/buffer.c:123:9: warning: function 'pm_buffer_append_format' might be a candidate for 'gnu_printf' format attribute [-Wsuggest-attribute=format]
  123 |         vsnprintf(buffer->value + cursor, length, format, arguments);
      |         ^~~~~~~~~
```

https://github.com/ruby/prism/commit/72da47973e

prism/compiler/format.h

@@ -4,6 +4,8 @@
 #ifndef PRISM_COMPILER_FORMAT_H
 #define PRISM_COMPILER_FORMAT_H
 
+#include <stdio.h>
+
 /**
  * Certain compilers support specifying that a function accepts variadic
  * parameters that look like printf format strings to provide a better developer