[roll] Roll fuchsia [hvdcp_opti] Fix ReadWriteBytesFile so it actually stores data

Original-Bug: 465183573

Test: tested on Sorrel that qbg_context is not empty

Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1442488
Original-Revision: 70415836dbdadc8e1fe1d03367faceae0bfa582d
GitOrigin-RevId: ddb7e230f4c14e2fa059b7543bb6d0abc20431a8
Change-Id: I5e2ee70fef780709d075e4b092c0a3737fa12c00

Author: Ruby Zhuang

stem

@@ -7,7 +7,7 @@
             manifest="manifests/platform"
             root=""
             remote="https://fuchsia.googlesource.com/fuchsia"
-            revision="40b4419921a1c500372bb42805c65721688070f8"/>
+            revision="70415836dbdadc8e1fe1d03367faceae0bfa582d"/>
   </imports>
   <projects>
     <project name="cobalt"