Fix file cleans up sincedb entry

Add `ExpectationNotMetError` to the arguments to `Stud.try`. Without this,
the retry logic does not trigger, leading to flakiness in this test as not
enough time has elapsed for the sincedb entry to be cleaned up

Author: robbavey

spec/inputs/file_read_spec.rb

@@ -338,7 +338,7 @@
       sincedb_content = File.read(sincedb_path).strip
       expect( sincedb_content ).to_not be_empty
 
-      Stud.try(3.times) do
+      Stud.try(3.times, RSpec::Expectations::ExpectationNotMetError) do
         sleep(1.5) # > sincedb_clean_after
 
         sincedb_content = File.read(sincedb_path).strip