Add a message in the update dialog about not using pip if Spyder is running under Anaconda/Miniconda

[ccordoba12]

@andfoy, the message should detect if Spyder is running under Anaconda or Miniconda and then it should warn users in our Update dialog like this:

Important note: If you are using Spyder with Anaconda or Miniconda, please don't use pip to update it because that will (most probably) break your installation.

Instead, please wait until new conda packages are made available and use conda update spyder to do it.