White space in CSV annotations cause Invalid Argument Errors

More of a nit than a critical bug. Take an example annotation such as:

```
#datatype measurement, double, double, double
measurement,x,y,z
demo,-0.514,0.070,1.672
```

executing `influx write ... ` will return "unsupported data type ' double'"

This can be remediated by simply removing the whitespace from the annotation row:
`#datatype measurement,double,double,double`

I wonder if there's a quick fix in [normalizeNumberString](https://github.com/influxdata/influx-cli/blob/35279515e98a1844338a6f8d03e10c0fd864a599/pkg/csv2lp/data_conversion.go#L95)

Start in pkg/csv2lp/data_conversion.go at normalizeNumberString, which the issue identifies as a possible entry point for handling whitespace in CSV annotations. Reproduce the sample with `influx write ...`, then verify that spaces after commas in the #datatype row are accepted and no longer produce an unsupported data type error.

Written by the indexing model from the issue text.