CI: Change tilemap source from Stamen to OpenStreetMap (#2701)

Author: weiji14

pygmt/tests/baseline/test_tilemap_no_clip_False.png.dvc

@@ -1,4 +1,4 @@
 outs:
-- md5: 9317080021b0ce6f3b9ea6d17feece00
-  size: 23275
+- md5: e2a9a57f61bdca0c21ddec3e1ae5d819
+  size: 16595
   path: test_tilemap_no_clip_False.png

pygmt/tests/baseline/test_tilemap_no_clip_True.png.dvc

@@ -1,4 +1,4 @@
 outs:
-- md5: 83e6119b2351f9d472ca7e3cc45388c3
-  size: 60984
+- md5: 86ce085faad17433dfabba675d0379ee
+  size: 38836
   path: test_tilemap_no_clip_True.png

pygmt/tests/baseline/test_tilemap_ogc_wgs84.png.dvc

@@ -1,4 +1,4 @@
 outs:
-- md5: 3de0555d86aca49b92425c8d5272a934
-  size: 59286
+- md5: 6da0601f305a6c3391e4a1aa0aee6173
+  size: 37139
   path: test_tilemap_ogc_wgs84.png

pygmt/tests/baseline/test_tilemap_web_mercator.png.dvc

@@ -1,4 +1,4 @@
 outs:
-- md5: a76d9a9a1890d6b1345305eaea598bc3
-  size: 122195
+- md5: 2965f6711c5878014491c7e6f791048e
+  size: 62077
   path: test_tilemap_web_mercator.png

pygmt/tests/test_tilemap.py

@@ -17,6 +17,7 @@ def test_tilemap_web_mercator():
     fig.tilemap(
         region=[-20000000.0, 20000000.0, -20000000.0, 20000000.0],
         zoom=0,
+        source=contextily.providers.OpenStreetMap.Mapnik,
         lonlat=False,
         frame="afg",
     )
@@ -31,7 +32,11 @@ def test_tilemap_ogc_wgs84():
     """
     fig = Figure()
     fig.tilemap(
-        region=[-180.0, 180.0, -90, 90], zoom=0, frame="afg", projection="R180/5c"
+        region=[-180.0, 180.0, -90, 90],
+        zoom=0,
+        source=contextily.providers.OpenStreetMap.Mapnik,
+        frame="afg",
+        projection="R180/5c",
     )
     return fig
 
@@ -47,6 +52,7 @@ def test_tilemap_no_clip(no_clip):
     fig.tilemap(
         region=[-180.0, 180.0, -90, 0.6886],
         zoom=0,
+        source=contextily.providers.OpenStreetMap.Mapnik,
         frame="afg",
         projection="H180/5c",
         no_clip=no_clip,