drop obsolete workaround for 6th gen Pixels

6th gen Pixels initially didn't declare support for the attest key
feature despite shipping support for it. This is no longer relevant
since the minimum supported OS version has been raised so it's not
possible to encounter the issue anymore.

Author: thestinger

app/src/main/java/app/attestation/auditor/AttestationProtocol.java

@@ -289,12 +289,6 @@ boolean hasPogoPins() {
             "Pixel 9a",
             "Pixel 10").contains(Build.MODEL);
 
-    // Pixel 6, Pixel 6 Pro and Pixel 6a forgot to declare the attest key feature when it shipped in Android 12
-    private static final boolean alwaysHasAttestKey = ImmutableSet.of(
-            "Pixel 6",
-            "Pixel 6 Pro",
-            "Pixel 6a").contains(Build.MODEL);
-
     private static final ImmutableMap<String, DeviceInfo> fingerprintsCustomOS = ImmutableMap
             .<String, DeviceInfo>builder()
             // GrapheneOS
@@ -1389,7 +1383,7 @@ static AttestationResult generateSerialized(final Context context, final byte[]
         final boolean hasPersistentKey = keyStore.containsAlias(persistentKeystoreAlias);
         final String attestationKeystoreAlias;
         final boolean useStrongBox;
-        final boolean canUseAttestKey = (alwaysHasAttestKey || pm.hasSystemFeature(PackageManager.FEATURE_KEYSTORE_APP_ATTEST_KEY));
+        final boolean canUseAttestKey = pm.hasSystemFeature(PackageManager.FEATURE_KEYSTORE_APP_ATTEST_KEY);
         final boolean useAttestKey;
         if (hasPersistentKey) {
             final String freshKeyStoreAlias = statePrefix + KEYSTORE_ALIAS_FRESH;