Remove codec libs from base_system.mk

- libstagefright_enc_common
- libstagefright_amrnb_common

Bug: 141885505
Test: build and boot.
      Checked libstagefright_enc_common.so doesn't exist in /system/lib64.
      libstagefright_amrnb_common.so is still there because other system
      module, librtp_jni.so, is using it, but there is no reason to keep
      this in base_system.mk.

Change-Id: I43692b50bd23e0b857606b42cb000c8566489dd6
diff --git a/target/product/base_system.mk b/target/product/base_system.mk
index 4e33d23..ec373db 100644
--- a/target/product/base_system.mk
+++ b/target/product/base_system.mk
@@ -174,8 +174,6 @@
     libspeexresampler \
     libsqlite \
     libstagefright \
-    libstagefright_amrnb_common \
-    libstagefright_enc_common \
     libstagefright_foundation \
     libstagefright_omx \
     libstdc++ \