Exclude "expected" files from linting

Those files are part of tests and hold what should be the output of the
compiler. If they are included in the linting, warnings will be emitted
when one of the tests in which the compiler outputs a line with trailing
whitespace is edited, which is not desirable.

.github/linters/.ecrc

@@ -1,4 +1,5 @@
 {
+  "Exclude" : ["expected"],
   "Disable": {
     "IndentSize": true,
     "Indentation": true