Rename const to kFrameTimelinesCapacity

From `kFrameTimelinesLength`.

Bug: 270612751
Test: build
Change-Id: I83e61a19254ab4a63479a2004124cfd2c082da35
diff --git a/libs/gui/tests/VsyncEventData_test.cpp b/libs/gui/tests/VsyncEventData_test.cpp
index 6e039ee..a2138f2 100644
--- a/libs/gui/tests/VsyncEventData_test.cpp
+++ b/libs/gui/tests/VsyncEventData_test.cpp
@@ -47,7 +47,7 @@
     ASSERT_EQ(data.vsync.frameInterval, data2.vsync.frameInterval);
     ASSERT_EQ(data.vsync.preferredFrameTimelineIndex, data2.vsync.preferredFrameTimelineIndex);
     ASSERT_EQ(data.vsync.frameTimelinesLength, data2.vsync.frameTimelinesLength);
-    for (int i = 0; i < VsyncEventData::kFrameTimelinesLength; i++) {
+    for (int i = 0; i < VsyncEventData::kFrameTimelinesCapacity; i++) {
         ASSERT_EQ(data.vsync.frameTimelines[i].vsyncId, data2.vsync.frameTimelines[i].vsyncId);
         ASSERT_EQ(data.vsync.frameTimelines[i].deadlineTimestamp,
                   data2.vsync.frameTimelines[i].deadlineTimestamp);