Follow error prone recommendation

In bluetooth/Utils.java:
```
247: warning:  The local variable 'uuid' is never read.
        UUID uuid;
             ^
351: warning:  Method enforceCdmAssociation() annotated [none] but too narrow;
invokes method requiring {allOf=[android.permission.MANAGE_COMPANION_DEVICES]}
        for (Association association : cdm.getAllAssociations()) {
                                                             ^
855: warning:  Private method 'isAppOppAllowed' is never used.
    private static boolean isAppOppAllowed(AppOpsManager appOps,
                           ^
862: warning:  `millisecond` is very close to the parameter `milliseconds`
     * Converts {@code millisecond} to unit. Each unit is 0.625 millisecond.
                ^
987: warning:  Must immediately define a try-finally block after Binder.clearCallingIdentity()
        final long ident = Binder.clearCallingIdentity();
                                                      ^
```

Bug: 236759221
Test: m RUN_ERROR_PRONE=true Bluetooth
Change-Id: I2163f7f5c5eab99f2a1ba2bcc3aedc38867fcd04