Update existing conda environments and templates to remove defaults channel

[jashapiro]

As part of #705, we should update all existing conda environment.yml and conda-lock.yml files to not include the defaults channel, to remove potential reliance on Anaconda licensing for end users.

When updating conda-lock.yml files, this will likely require deleting and recreating the files, as conda-lock does not seem to like when the channel list changes between updates.

The modules currently affected by this are:

• cell-type-ewings
• doublet-detection
• hello-python
• metacells
• templates