doc: two typos

* doc/mainpage.dox, doc/org/tut01.org: Here.

doc/mainpage.dox

@@ -25,7 +25,7 @@
 /// \li spot::twa             Base class for Transition-based
 ///                           ω-Automata.
 /// \li spot::translator      Convert a spot::formula into a
-///                           spot::tgba.
+///                           spot::twa.
 /// \li spot::kripke          Base class for Kripke structures.
 /// \li spot::twa_product     On-the-fly product of two spot::twa.
 /// \li spot::emptiness_check Base class for all emptiness-check algorithms

doc/org/tut01.org

@@ -35,7 +35,7 @@ they are considered as atomic propositions in all the other syntaxes.)
 
 * Python bindings
 
-Here are the same operation in Python
+Here are the same operations in Python
 
 #+BEGIN_SRC python :results output :exports both
 import spot