Put conda-forge first in the list of channels

Otherwise conda picks outdated version of libssh2 from biobuilds, which links to
non-existing libopenssl.so.1.0.0

.github/workflows/gh-ci.yaml

@@ -99,7 +99,11 @@ jobs:
         python-version: ${{ matrix.python-version }}
         auto-update-conda: true
         channel-priority: flexible
-        channels: biobuilds, conda-forge
+        # The order of these channel matters: both provide "fundamental"
+        # software (curl, ssh, ...), but the version in biobuilds are very
+        # outdated. This can lead to problem when loading shared libraries,
+        # see https://github.com/MDAnalysis/mdanalysis/pull/3126#issuecomment-813112080
+        channels: conda-forge, biobuilds
         add-pip-as-python-dependency: true
         # TODO: mamba causes pip to segfault, switch when fixed
         #mamba-version: "*"
@@ -191,7 +195,7 @@ jobs:
         python-version: 3.7
         auto-update-conda: true
         channel-priority: flexible
-        channels: biobuilds, conda-forge
+        channels: conda-forge, biobuilds
         add-pip-as-python-dependency: true
         architecture: x64