Remove documentation of space coercions

I'll leave the functionality in place as a DWIM, but this is a plugin
for working with words and identifiers, not phrases, and I don't want
the documentation to give an impression to the contrary.

References: #66

doc/abolish.txt

@@ -159,8 +159,6 @@ characters:
   k:       kebab-case (not usually reversible; see |abolish-coercion-reversible|)
   -:       dash-case (aka kebab-case)
   .:       dot.case (not usually reversible; see |abolish-coercion-reversible|)
-  <space>: space case (not usually reversible; see |abolish-coercion-reversible|)
-  t:       Title Case (not usually reversible; see |abolish-coercion-reversible|)
 
 For example, cru on a lowercase word is a slightly easier to type equivalent
 to gUiw.