Fix typo (#52)

test/spec.txt

@@ -419,7 +419,7 @@ Normally the `>` that begins a block quote may be followed
 optionally by a space, which is not considered part of the
 content.  In the following case `>` is followed by a tab,
 which is treated as if it were expanded into spaces.
-Since one of theses spaces is considered part of the
+Since one of these spaces is considered part of the
 delimiter, `foo` is considered to be indented six spaces
 inside the block quote context, so we get an indented
 code block starting with two spaces.
@@ -9840,4 +9840,3 @@ closers:
 
 After we're done, we remove all delimiters above `stack_bottom` from the
 delimiter stack.
-