Update latest version in README.md (#809)

2.5.5 has been out already for a few weeks
diff --git a/README.md b/README.md
index ce3463b..66badba 100644
--- a/README.md
+++ b/README.md
@@ -35,6 +35,6 @@
 
 ```groovy
 dependencies {
-  implementation 'com.airbnb.android:lottie:2.5.4'
+  implementation 'com.airbnb.android:lottie:2.5.5'
 }
 ```