Fix typo at README.md (#5061)

mikelsr · JukkaL · commit a38928061809 · 2018-05-16T06:58:46.000-04:00
diff --git a/README.md b/README.md
@@ -136,7 +136,7 @@ this:
 
     $ python3 -m pip install -U mypy
 
-This should automatically installed the appropriate version of
+This should automatically install the appropriate version of
 mypy's parser, typed-ast.  If for some reason it does not, you
 can install it manually:
 
