Never expand proc_type attribute

It's used in build-time tests and in CTS.

Bug: 78898770
Test: build user-build
Change-Id: I254bf4d7ed0c0cb029b55110ceec982b84e4a91b
(cherry picked from commit beeb122405070a5b4cee326a0cdae92a1a791fbc)

prebuilts/api/28.0/public/attributes

@@ -38,6 +38,7 @@ attribute vendor_file_type;
 
 # All types used for procfs files.
 attribute proc_type;
+expandattribute proc_type false;
 
 # All types used for sysfs files.
 attribute sysfs_type;

public/attributes

@@ -38,6 +38,7 @@ attribute vendor_file_type;
 
 # All types used for procfs files.
 attribute proc_type;
+expandattribute proc_type false;
 
 # All types used for sysfs files.
 attribute sysfs_type;