Revert "Fix MediaDrm security level APIs"

This reverts commit 52d274d3428a26c3130fd72dfcc2be2f3058d56e.

Reason for revert: Build cop here. The CL topic that I'm reverting broke several builds: Drm.h's openSession(Vector<uint8_t> &sessionId) hides overloaded virtual function openSession(DrmPlugin::SecurityLevel securityLevel, ..) from IDrm.h.

https://android-build.googleplex.com/builds/submitted/4598692/full-eng/latest/view/logs/build_error.log

Change-Id: I6c1029e615ea9f418d265c75db28981036c98ee8
diff --git a/headers/media_plugin/media/drm/DrmAPI.h b/headers/media_plugin/media/drm/DrmAPI.h
index c44a1f6..0a3a356 100644
--- a/headers/media_plugin/media/drm/DrmAPI.h
+++ b/headers/media_plugin/media/drm/DrmAPI.h
@@ -148,9 +148,6 @@
         enum SecurityLevel {
             // Failure to access security level, an error occurred
             kSecurityLevelUnknown,
-            // The maximum security level of the device. This is the default when
-            // a session is opened if no security level is specified
-            kSecurityLevelMax,
             // Software-based whitebox crypto
             kSecurityLevelSwSecureCrypto,
             // Software-based whitebox crypto and an obfuscated decoder