Update fig.solar baseline images for GMT 6.2.0rc1

pygmt/tests/baseline/test_solar_set_terminator_datetime.png.dvc

@@ -1,4 +1,4 @@
 outs:
-- md5: 0a7f4959b500b6fa3a560a6368db0f90
-  size: 25982
+- md5: 0f8baadcf84e0222b6a42a2525277c78
+  size: 25000
   path: test_solar_set_terminator_datetime.png

pygmt/tests/baseline/test_solar_terminators.png.dvc

@@ -1,4 +1,4 @@
 outs:
-- md5: 54c92bea64e0fc76c62601cb6131f22e
-  size: 44160
+- md5: 9854a8041fe4c5d8b3832446b77fb482
+  size: 41749
   path: test_solar_terminators.png

pygmt/tests/test_solar.py

@@ -8,6 +8,10 @@
 from pygmt.exceptions import GMTInvalidInput
 
 
+@pytest.mark.xfail(
+    reason="Flaky test only passes with pytest on single module"
+    "See https://github.com/GenericMappingTools/pygmt/issues/1242"
+)
 @pytest.mark.mpl_image_compare
 def test_solar_terminators():
     """
@@ -39,6 +43,10 @@ def test_solar_terminators():
     return fig
 
 
+@pytest.mark.xfail(
+    reason="Flaky test only passes with pytest on single module"
+    "See https://github.com/GenericMappingTools/pygmt/issues/1242"
+)
 @pytest.mark.mpl_image_compare(filename="test_solar_set_terminator_datetime.png")
 @pytest.mark.parametrize(
     "terminator_datetime",
@@ -104,6 +112,10 @@ def test_invalid_datetime():
         )
 
 
+@pytest.mark.xfail(
+    reason="Flaky test only passes with pytest on single module"
+    "See https://github.com/GenericMappingTools/pygmt/issues/1242"
+)
 @pytest.mark.mpl_image_compare(filename="test_solar_set_terminator_datetime.png")
 def test_solar_default_terminator():
     """