doc: fix typo and add bold weight to first mention of important terms…

… in r.geomorphon manual page (OSGeo#4831)

* fix typo

raster/r.geomorphon/r.geomorphon.html

@@ -35,7 +35,7 @@ <h3>What is geomorphon:</h3>
 
 <p> There are 3**8 = 6561 possible ternary patterns (8-tuples). However by
 eliminating all patterns that are results of either rotation or reflection
-of other patterns wa set of 498 patterns remain referred as geomorphons.
+of other patterns we get a set of 498 patterns remain referred as geomorphons.
 This is a comprehensive and exhaustive set of idealized landforms that are
 independent of the size, relief, and orientation of the actual landform.