Remove TODO for b/112462307

b/112462307 is fixed now, remove the TODO.

Bug: 112462307
Test: dexlist out/soong/.intermediates/bootable/recovery/updater_sample/SystemUpdaterSample/android_common/dex/classes.dex | grep getUpdaterState
Change-Id: I19cb93a74b714967e4bab2964e229a0ab0a15676

updater_sample/Android.bp

@@ -24,11 +24,9 @@ android_app {
     ],
 
     optimize: {
-        // TODO(b/112462307): proguard_flags_files is not picked up by Soong.
-        // proguard_flags_files: [
-        //     "proguard.flags",
-        // ],
-        enabled: false,
+        proguard_flags_files: [
+            "proguard.flags",
+        ],
     },
 
     resource_dirs: ["res"],