Fix swapped certificate and private key in soong apps

The .x509.pem file should be in CERTIFICATE, and the .pk8 file
in PRIVATE_KEY.

Bug: 70669383
Test: examine apkcerts.txt
Change-Id: I480f19be2efbbd72ea23ebd681f312b94accfd7a
diff --git a/core/soong_app_prebuilt.mk b/core/soong_app_prebuilt.mk
index a49f835..633ef0c 100644
--- a/core/soong_app_prebuilt.mk
+++ b/core/soong_app_prebuilt.mk
@@ -63,8 +63,8 @@
 
 PACKAGES := $(PACKAGES) $(LOCAL_MODULE)
 ifdef LOCAL_CERTIFICATE
-  PACKAGES.$(LOCAL_MODULE).PRIVATE_KEY := $(LOCAL_CERTIFICATE)
-  PACKAGES.$(LOCAL_MODULE).CERTIFICATE := $(patsubst %.x509.pem,%.pk8,$(LOCAL_CERTIFICATE))
+  PACKAGES.$(LOCAL_MODULE).CERTIFICATE := $(LOCAL_CERTIFICATE)
+  PACKAGES.$(LOCAL_MODULE).PRIVATE_KEY := $(patsubst %.x509.pem,%.pk8,$(LOCAL_CERTIFICATE))
 endif
 
 ifndef LOCAL_IS_HOST_MODULE