Make hidl.manager optional in default device matrix

It is no longer required with Android U, so change the default device
compatibility matrix to reflect that.

Test: boot cuttlefish with and without hwservicemanager
Bug: 218588089
Change-Id: I43d918e9531034f7b28fbe592563e268e7d3988a

vintfdata/device_compatibility_matrix.default.xml

diff --git a/vintfdata/device_compatibility_matrix.default.xml b/vintfdata/device_compatibility_matrix.default.xml
index eaa513e..70d23e2 100644
--- a/vintfdata/device_compatibility_matrix.default.xml
+++ b/vintfdata/device_compatibility_matrix.default.xml
@@ -1,5 +1,5 @@
 <compatibility-matrix version="1.0" type="device">
-    <hal format="hidl" optional="false">
+    <hal format="hidl" optional="true">
         <name>android.hidl.manager</name>
         <version>1.0</version>
         <interface>