More mamba install recommendations

Update a few more `conda` references to `mamba` in the main README and other locations that were missed out in #2385.

.github/ISSUE_TEMPLATE/bump_gmt_checklist.md

@@ -10,7 +10,7 @@ assignees: ''
 :tada: [GMT X.Y.Z](https://github.com/GenericMappingTools/gmt/releases/tag/X.Y.Z) has been released! It is installable from the
 [conda-forge channel](https://anaconda.org/conda-forge/gmt/files) using the following command:
 
-`conda install -c conda-forge gmt=X.Y.Z`
+`mamba install -c conda-forge gmt=X.Y.Z`
 
 <!-- Please add specific checklist items for the tests, xfail pytest markers, and deprecated syntax that need to be updated. -->
 

.github/workflows/style_checks.yaml

@@ -18,7 +18,7 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v3.3.0
 
-      # Setup Miniconda
+      # Setup Python
       - name: Set up Python
         uses: actions/setup-python@v4.5.0
         with:

README.rst

@@ -92,13 +92,13 @@ Quickstart
 Installation
 ++++++++++++
 
-Simple installation using `conda <https://docs.conda.io/projects/conda/en/latest/user-guide/index.html>`__::
+Simple installation using `mamba <https://mamba.readthedocs.org/>`__::
 
-    conda install --channel conda-forge pygmt
+    mamba install --channel conda-forge pygmt
 
-If you use `mamba <https://mamba.readthedocs.org/>`__::
+If you use `conda <https://docs.conda.io/projects/conda/en/latest/user-guide/index.html>`__::
 
-    mamba install --channel conda-forge pygmt
+    conda install --channel conda-forge pygmt
 
 For other ways to install ``pygmt``, see `full installation instructions <https://www.pygmt.org/latest/install.html>`__.
 

pygmt/__init__.py

@@ -187,12 +187,12 @@ def test(doctest=True, verbose=True, coverage=False, figures=True):
     Run the test suite.
 
     Uses `pytest <http://pytest.org/>`__ to discover and run the tests. If you
-    haven't already, you can install it with `conda
-    <http://conda.pydata.org/>`__ or `pip <https://pip.pypa.io/en/stable/>`__.
+    haven't already, you can install it with `mamba
+    <https://mamba.readthedocs.org/>`__ or `pip
+    <https://pip.pypa.io/en/stable/>`__.
 
     Parameters
     ----------
-
     doctest : bool
         If ``True``, will run the doctests as well (code examples that start
         with a ``>>>`` in the docs).