View aggregation examples modified to remove unsupported things

[cijothomas]

The current spec for View does not allow specifying temporality (cumulative/delta) on aggregation, and it is only allowed along with MetricReader. This PR is modifying the examples to remove the unsupported capabilities, to avoid confusion.

[jmacd]

I'd like it to be clear how the reader should interpret the first argument of the reader. I want it to explain this is the treatment for synchronous instruments, which the SDK has control over. Asynchronous instruments should be exported in their natural temporality, and we do not want to encourage anyone to expect Cumulative-to-Delta conversion inside the SDK.

[cijothomas]

Asynchronous instruments should be exported in their natural temporality, and we do not want to encourage anyone to expect Cumulative-to-Delta conversion inside the S

Don't think this example need to talk about it. There is spec already existing here https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/sdk.md#metricreader which talk about temporality, cumulative->delta conversions etc.

[jmacd]

Don't think this example need to talk about it.

Later in the SDK specification, we write:

The SDK SHOULD provide a way to allow the preferred Aggregation
Temporality to be specified for a MetricReader
instance during the setup

But the reader will not have reached that point in the specification yet, and I want it to be clear what this means.

I changed my suggestion from "using" to "preferring" which is more correct.

[jmacd]

See #2314

See #2314