Apply suggestions from code review

Co-authored-by: Wei Ji <23487320+weiji14@users.noreply.github.com>

Author: seisman

pygmt/helpers/caching.py

@@ -18,8 +18,8 @@ def cache_data():
         "@earth_gebcosi_01d_g",
         "@earth_gebcosi_15m_p",
         "@earth_geoid_01d_g",
-        "@earth_mag4km_01d_g",
         "@earth_mag_01d_g",
+        "@earth_mag4km_01d_g",
         "@earth_mask_01d_g",
         "@earth_relief_01d_g",
         "@earth_relief_01d_p",
@@ -55,8 +55,8 @@ def cache_data():
         "@N35E135.earth_relief_03s_g.nc",
         "@N37W120.earth_relief_03s_g.nc",
         "@S15W105.earth_synbath_30s_p.nc",
-        "@S90E000.earth_wdmam_03m_g.nc",
         "@N00W030.earth_vgg_01m_p.nc",
+        "@S90E000.earth_wdmam_03m_g.nc",
         "@N00W030.mars_relief_01m_g.nc",
         "@N00W030.mercury_relief_01m_p.nc",
         "@N00W030.moon_relief_01m_p.nc",