Bump pandas to 2.0 in mindeps build (#8743)

Author: jrbourbeau

.github/workflows/tests.yaml

@@ -83,12 +83,12 @@ jobs:
           - os: ubuntu-latest
             environment: mindeps
             label: pandas
-            extra_packages: [numpy=1.21, pandas=1.3, pyarrow=7, pyarrow-hotfix]
+            extra_packages: [numpy=1.21, pandas=2.0, pyarrow=7, pyarrow-hotfix]
             partition: "ci1"
           - os: ubuntu-latest
             environment: mindeps
             label: pandas
-            extra_packages: [numpy=1.21, pandas=1.3, pyarrow=7, pyarrow-hotfix]
+            extra_packages: [numpy=1.21, pandas=2.0, pyarrow=7, pyarrow-hotfix]
             partition: "not ci1"
 
           - os: ubuntu-latest

distributed/protocol/tests/test_highlevelgraph.py

@@ -6,12 +6,12 @@
 
 np = pytest.importorskip("numpy")
 pd = pytest.importorskip("pandas")
+dd = pytest.importorskip("dask.dataframe")
+da = pytest.importorskip("dask.array")
 
 from numpy.testing import assert_array_equal
 
 import dask
-import dask.array as da
-import dask.dataframe as dd
 
 from distributed.diagnostics import SchedulerPlugin
 from distributed.utils_test import gen_cluster