[style] Change tag type to hb_style_tag_t

https://github.com/harfbuzz/harfbuzz/pull/3201#discussion_r708914354
diff --git a/src/hb-style.cc b/src/hb-style.cc
index 23153dd..58fde1b 100644
--- a/src/hb-style.cc
+++ b/src/hb-style.cc
@@ -73,12 +73,11 @@
  * Since: REPLACEME
  **/
 float
-hb_style_get_value (hb_font_t *font, hb_tag_t tag)
+hb_style_get_value (hb_font_t *font, hb_style_tag_t style_tag)
 {
-  if (unlikely (tag == HB_STYLE_TAG_SLANT_RATIO))
+  if (unlikely (style_tag == HB_STYLE_TAG_SLANT_RATIO))
     return _hb_angle_to_ratio (hb_style_get_value (font, HB_STYLE_TAG_SLANT_ANGLE));
 
-  hb_style_tag_t style_tag = (hb_style_tag_t) tag;
   hb_face_t *face = font->face;
 
 #ifndef HB_NO_VAR
diff --git a/src/hb-style.h b/src/hb-style.h
index 352f565..5af581f 100644
--- a/src/hb-style.h
+++ b/src/hb-style.h
@@ -72,7 +72,7 @@
 
 
 HB_EXTERN float
-hb_style_get_value (hb_font_t *font, hb_tag_t style_tag);
+hb_style_get_value (hb_font_t *font, hb_style_tag_t style_tag);
 
 HB_END_DECLS