[ledger] Add stored corpus for the btree encoding fuzztest

LE-644 #done

Change-Id: I2f36418a868c85527a320db5b31b92e75d17a5b8
Test: fx fuzz start ledger still works
diff --git a/bin/ledger/storage/impl/btree/BUILD.gn b/bin/ledger/storage/impl/btree/BUILD.gn
index 98d7983..5b88d5e 100644
--- a/bin/ledger/storage/impl/btree/BUILD.gn
+++ b/bin/ledger/storage/impl/btree/BUILD.gn
@@ -112,4 +112,7 @@
     ":lib",
     "//peridot/bin/ledger/storage/public",
   ]
+  corpora = [
+    "848002de6109d94118c57d79b2a8c0cfbd16ba8691bb390e3eb7437089ad99cc"
+  ]
 }