Remove the parentheses around image->alphaPlane

The parentheses can be omitted.
diff --git a/src/avif.c b/src/avif.c
index eb5bbf4..a50d21b 100644
--- a/src/avif.c
+++ b/src/avif.c
@@ -439,7 +439,7 @@
         }
         return (image->width + formatInfo.chromaShiftX) >> formatInfo.chromaShiftX;
     }
-    if ((channel == AVIF_CHAN_A) && (image->alphaPlane)) {
+    if ((channel == AVIF_CHAN_A) && image->alphaPlane) {
         return image->width;
     }
     return 0;
@@ -458,7 +458,7 @@
         }
         return (image->height + formatInfo.chromaShiftY) >> formatInfo.chromaShiftY;
     }
-    if ((channel == AVIF_CHAN_A) && (image->alphaPlane)) {
+    if ((channel == AVIF_CHAN_A) && image->alphaPlane) {
         return image->height;
     }
     return 0;