Fix mypy regex

Author: kylebarron

matchers/mypy.json

@@ -4,7 +4,7 @@
       "code": "E",
       "pattern": [
         {
-          "regexp": "^(\\S*)(\\d+):(\\d+): ([a-z]+): (.*)$",
+          "regexp": "^(\\S*):(\\d+):(\\d+): ([a-z]+): (.*)$",
           "file": 1,
           "column": 3,
           "line": 2,