CI: Cache two tiles of remote data used in tests (#4392)

Author: seisman

pygmt/helpers/caching.py

@@ -82,8 +82,10 @@ def cache_data() -> None:
         "@S30W060.earth_mag_02m_p.nc",
         "@S90E000.earth_mag_05m_g.nc",
         "@S30W120.earth_mag4km_02m_p.nc",
+        "@N00W030.earth_mss_01m_g.nc",
         "@N30E090.earth_mss_01m_g.nc",
         "@S90E000.earth_mss_05m_g.nc",
+        "@N00W030.earth_ndefl_01m_p.nc",
         "@N30E090.earth_ndefl_01m_p.nc",
         "@N00W090.earth_relief_03m_p.nc",
         "@N00E135.earth_relief_30s_g.nc",