Fix a typo

Co-authored-by: Yvonne Fröhlich <94163266+yvonnefroehlich@users.noreply.github.com>

Author: seisman

examples/gallery/symbols/patterns.py

@@ -22,7 +22,7 @@
 GMT provides 90 predefined 1-bit patterns, which are numbered from 1 to 90. In addition,
 custom 1-, 8-, or 24-bit image raster files can also be used as patterns.
 
-Theses patterns can be specified via the :class:`pygmt.params.Pattern` class. The
+These patterns can be specified via the :class:`pygmt.params.Pattern` class. The
 patterns can be customized with different resolution and different foreground and
 background colors. The foreground and background colors can also be inverted.
 """