Include <algorithm> in FixedCountBufferUtils.h

Some IWYU since clang headers are becoming less lenient.

Bug: b/226311807
Bug: cl/436707135
Change-Id: I1a439c57c0e003204f72b9874c001ff5357cd1a8
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/523857
Auto-Submit: Ben Wagner <bungeman@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>

src/gpu/tessellate/FixedCountBufferUtils.h

@@ -10,6 +10,8 @@
 
 #include "include/core/SkPaint.h"
 
+#include <algorithm>
+
 namespace skgpu {
 
 struct VertexWriter;