TST Remove freeimage from test dependencies

OTOH, freeimage and imread to CI test env. This way, they are tested on CI, but not required for wheel building and others

Also, upgrade deprecated actions/checkout@v2 action (to
actions/checkout@v4)

.github/workflows/test-python-package-with-conda.yml

@@ -100,7 +100,7 @@ jobs:
               numpy-version: '1.25'
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - uses: mamba-org/setup-micromamba@v1
       with:
         cache-environment: true
@@ -112,6 +112,7 @@ jobs:
       shell: bash -l {0}
       run: |
         micromamba install --file tests-requirements.txt --name mahotas_test_env
+        micromamba install --name mahotas_test_env freeimage imread
     - name: Build
       shell: bash -l {0}
       run: |

tests-requirements.txt

@@ -1,6 +1,5 @@
 matplotlib
 pip
-freeimage
 coveralls
 pytest<=8.1.1
 scipy