Update jacoco's README.android.

The README was updated in http://ag/3492180 but not in
http://ag/3505896. This change brings it up to date. (Only a minor
change, but it seems better to be accurate.)

Bug: 64836607
Test: N/A
Change-Id: I32e161fec14eee35154f4d754ab2f14e160923c8
diff --git a/README.android b/README.android
index 8386674..8fa2b90 100644
--- a/README.android
+++ b/README.android
@@ -17,7 +17,7 @@
 3) Change the runtime to reduce dependencies on core libraries.
    Previously, Offline's static initializer would eagerly create an
    Agent, a process which has lots of dependencies. With this change,
-   Offline only eagerly creates an ExecutionDataStore, which is much
+   Offline only eagerly creates a Map<Long, ExecutionData>, which is much
    more lightweight. The Agent is only created when it's actually
    needed. This makes it possible to instrument a lot of more core
    libraries without creating a circular dependency at runtime.