Revert "first_stage_mount: Bind mount /system after switch root"

This reverts commit d7e6353a69f6cc0b66198eb0a2726abe0f655dcb.

Reason for revert: b/239574953 breaking emulator based test on g3

Change-Id: Ib7d17fe8383937c7764f6612cf89db4fb7e5a4d3
diff --git a/init/first_stage_mount.cpp b/init/first_stage_mount.cpp
index 1c0189b..4bbbc20 100644
--- a/init/first_stage_mount.cpp
+++ b/init/first_stage_mount.cpp
@@ -518,12 +518,6 @@
         return false;
     }
 
-    // Make /system a mountpoint so that adb-remount can move submounts under /system.
-    if (access("/system", F_OK) == 0 &&
-        mount("/system", "/system", nullptr, MS_BIND, nullptr) != 0) {
-        PLOG(WARNING) << "Failed to bind mount /system for overlayfs";
-    }
-
     return true;
 }