load_earth_magnatic_anomaly: Fix the description of resolution and re…

…gistration (#2328)

Co-authored-by: Will Schlitzer <[email protected]>

pygmt/datasets/earth_magnetic_anomaly.py

@@ -42,7 +42,8 @@ def load_earth_magnetic_anomaly(
         The grid resolution. The suffix ``d`` and ``m`` stand for
         arc-degrees and arc-minutes. It can be ``"01d"``, ``"30m"``,
         ``"20m"``, ``"15m"``, ``"10m"``, ``"06m"``, ``"05m"``, ``"04m"``,
-        ``"03m"``, or ``"02m"``.
+        ``"03m"``, or ``"02m"``. The ``"02m"`` resolution is not available for
+        ``data_source="wdmam"``.
 
     region : str or list
         The subregion of the grid to load, in the form of a list
@@ -53,7 +54,8 @@ def load_earth_magnetic_anomaly(
     registration : str
         Grid registration type. Either ``"pixel"`` for pixel registration or
         ``"gridline"`` for gridline registration. Default is ``"gridline"``
-        for all resolutions except ``"02m"`` which is ``"pixel"`` only.
+        for all resolutions except ``"02m"`` for ``data_source="emag2"`` or
+        ``data_source="emag2_4km"``, which are ``"pixel"`` only.
 
     data_source : str
         Select the source of the magnetic anomaly data.