Improve error for disallowed "manage -monitor" on local lake

[philrz]

Repro is with Zed commit bedcc95.

A community zync user was recently testing compaction for the first time and was confused when they found zed manage worked ok against a local lake accessed via filesystem but zed manage -monitor didn't. For instance:

$ zed -version
Version: v1.11.1-4-gbedcc95f

$ zed -lake lake init
lake created: file:///Users/phil/lake

$ zed -lake lake create -use foo
pool created: foo 2YJh52qipSPBKcuxB3TTkZGanGq
Switched to branch "main" on pool "foo"

$ zed -lake lake load ~/Desktop/sample.zng 
(2/1) 4910B/4910B 4910B/s 100.00%
2YJh6ttgCCQglN8JVDN82MIgPxc committed

$ zed -lake lake manage
{"level":"info","ts":1700249421.980949,"logger":"pool","msg":"updating pool","name":"foo","id":"2YJh52qipSPBKcuxB3TTkZGanGq","branch":"main","interval":60,"vectors":false}
{"level":"info","ts":1700249421.984308,"logger":"pool","msg":"compaction completed","name":"foo","id":"2YJh52qipSPBKcuxB3TTkZGanGq","branch":"main","interval":60,"vectors":false,"runs_found":0,"objects_compacted":0,"vectors_created":0}

$ zed -lake lake manage -monitor
cannot open connection on local lake

The wording implies that it could work on a local lake but cannot, when in actuality this combination is simply not yet supported. We should adjust the wording to make this more explicit (e.g., "'manage -monitor' not currently supported on local lakes").

[philrz]

Verified in Zed commit 8a48163.

Repeating the original repro steps, the error message is now improved.

$ zed -version
Version: v1.12.0-28-g8a48163f

...

$ zed -lake lake manage -monitor
monitor on local lake not supported

Thanks @mattnibs!