Removing selinux_android_prop_context_handle

This function hasn't been used for near two years.
Removing it to prevent confusion.

The last usage is removed in
commit I27dd391fc06a3c78e88a65c7931c84de1699f157

Bug: 137712473
Bug: 141871131
Test: boot the device
Change-Id: I9d26ca7375b49b98a1fc6fda38f1ef9fd3c3f563
5 files changed