Remove ProcFileReader from framework-connectivity-shared-srcs

The dependency in NetworkStatsFactory is removed, so it's no
longer needed.

Bug: 234315786
Test: m ; atest FrameworksNetTests
Change-Id: Ieec54c5b5cb679042e2d7aebe4005644352bdc62

core/java/Android.bp

@@ -170,8 +170,6 @@ filegroup {
         "com/android/internal/util/IndentingPrintWriter.java",
         "com/android/internal/util/MessageUtils.java",
         "com/android/internal/util/WakeupMessage.java",
-        // TODO: delete as soon as NetworkStatsFactory stops using
-        "com/android/internal/util/ProcFileReader.java",
     ],
 }