Proposal: update location slack channels to have a common prefix for discoverability

Currently, it looks like we have the following location related channels:

• #4corners
• #berlin
• #brazil
• #denver
• #dmv
• #france
• #holland
• #minnesota
• #nashville
• #netherlands
• #ny
• #philadelphia
• #poland
• #portugal
• #spain
• #sunshine_labbers
• #texas
• #uk
• #utah
• #valley

For discoverability, I propose that we prepend these with #loc_ similar to how we've grouped the #lang_ and #f_ channels.