[docs] Fix typo and minor text changes in MyFirstTypoFix

[kuhnel]

@xgupta @xzq0528 @gribozavr @meikeb
FYI, as you were working on this tutorial as well

llvm/docs/MyFirstTypoFix.rst

.. code:: console
    ********************
    Testing Time: 408.84s
    ********************
    Failing Tests (1):
        Clang :: SemaCXX/warn-infinite-recursion.cpp
 
 Well, that makes sense… and the test output suggests it's looking for
 the old string "call itself" and finding our new message instead.
+Note that more tests may fail in a similar way as new tests are
+added time to time.
 
 Let's fix it by updating the expectation in the test.
 
 .. code:: console
 
    $ vi ../clang/test/SemaCXX/warn-infinite-recursion.cpp
 
-Everywhere we see // expected-warning{{call itself}}, let's replace it
-with // expected-warning{{to understand recursion}}.
+Everywhere we see `// expected-warning{{call itself}}` (or something similar
+from the original warning text), let's replace it with
+`// expected-warning{{to understand recursion}}`.
 
 Now we could run **all** the tests again, but this is a slow way to
 iterate on a change! Instead, let's find a way to re-run just the
 specific test. There are two main types of tests in LLVM:
 
 -  **lit tests** (e.g. SemaCXX/warn-infinite-recursion.cpp).
 
 These are fancy shell scripts that run command-line tools and verify the
 output. They live in files like
 clang/**test**/FixIt/dereference-addressof.c. Re-run like this:
 
 .. code:: console
 
    $ bin/llvm-lit -v ../clang/test/SemaCXX/warn-infinite-recursion.cpp
 
--  **unit tests** (e.g. ToolingTests/ReplacementText.CanDeleteAllText)
+-  **unit tests** (e.g. ToolingTests/ReplacementTest.CanDeleteAllText)
 
 These are C++ programs that call LLVM functions and verify the results.
 They live in suites like ToolingTests. Re-run like this:
 
 .. code:: console
 
    $ ninja ToolingTests && tools/clang/unittests/Tooling/ToolingTests
-   --gtest_filter=ReplacementText.CanDeleteAllText
+   --gtest_filter=ReplacementTest.CanDeleteAllText
 
 
 Commit locally
 --------------
 
 We'll save the change to a local git branch. This lets us work on other
 things while the change is being reviewed. Changes should have a
 description, to explain to reviewers and future readers of the code why