Bump RiveRuntime iOS SDK to 6.20.4 (#270)

Fixes flaky autoplay harness tests. The 6.20.1 fix for "massive
timestamp delta on first frame" was causing the animation to jump
through its entire cycle in one frame, making ypos property change
detection unreliable. Verified with 100 consecutive test runs (0
failures).

Author: mfazekas

example/ios/Podfile.lock

@@ -2242,7 +2242,7 @@ PODS:
     - React-perflogger (= 0.80.3)
     - React-utils (= 0.80.3)
     - SocketRocket
-  - RiveRuntime (6.20.0)
+  - RiveRuntime (6.20.4)
   - RNCAsyncStorage (2.2.0):
     - boost
     - DoubleConversion
@@ -2422,7 +2422,7 @@ PODS:
     - RNWorklets
     - SocketRocket
     - Yoga
-  - RNRive (0.4.6):
+  - RNRive (0.4.7):
     - boost
     - DoubleConversion
     - fast_float
@@ -2450,7 +2450,7 @@ PODS:
     - ReactCodegen
     - ReactCommon/turbomodule/bridging
     - ReactCommon/turbomodule/core
-    - RiveRuntime (= 6.20.0)
+    - RiveRuntime (= 6.20.4)
     - SocketRocket
     - Yoga
   - RNScreens (4.18.0):
@@ -2935,12 +2935,12 @@ SPEC CHECKSUMS:
   ReactAppDependencyProvider: bd4d54d31d1a9e2eddff7675bb7628731a42b98c
   ReactCodegen: 8e8c7dc0113d08d218f409fbb2cd3b966b982e11
   ReactCommon: 04362bc6625a80fa21b174f527352db70e5ad06a
-  RiveRuntime: 12f860505e052a8b48c580f35f1d5d5cad6709b7
+  RiveRuntime: f99ddd1d4b6a420dea5943ff52502e8f92ae7a92
   RNCAsyncStorage: 1f04c8d56558e533277beda29187f571cf7eecb2
   RNCPicker: a0b804b489974349cde24b41b654ce9d5eefa504
   RNGestureHandler: 5b17f2ffba1909187924a248aaca7d077673d857
   RNReanimated: d9b3c88b7a722ce8129ca8c96abd06d822ed315e
-  RNRive: 63a8e07c3b2e1ebfdcef7dcba3efdd71e90e93a8
+  RNRive: fc8277cea345e59de9178dddb3b1729fcf8ef695
   RNScreens: f35bcc83b6e3a871635b1c28728e63c9560f159a
   RNWorklets: 7fb44cd32a491df4a4832cce2f3b0aaaf813956d
   SocketRocket: d4aabe649be1e368d1318fdf28a022d714d65748

package.json

@@ -65,7 +65,7 @@
   },
   "homepage": "https://github.com/rive-app/rive-nitro-react-native#readme",
   "runtimeVersions": {
-    "ios": "6.20.0",
+    "ios": "6.20.4",
     "android": "11.4.1"
   },
   "publishConfig": {