Change conda env name

[calispac]

As the title suggests this changes the name of the conda environment from "cta" to "lstchain".
I think "cta" is too generic. I hope this does not affects user who got the habit to do conda activate cta.

[calispac]

This is ready to be reviewed/accepted + eventually merged.

[vuillaut]

Hi.
I think you are right that cta is not well chosen.
However I would propose lst-dev to be inline with ctapipe and to avoid confusion of users new to conda and co, between the library and the environment.

[calispac]

Hi ! Ok thanks it is changed

[rlopezcoto]

what about lstchain-dev?

[vuillaut]

Seems good to me.
lst-dev is specific and short enough in my opinion.