[Defence] Update grammar

defense/slides.md

@@ -29,7 +29,7 @@
 * Q1: What is the role of edit filters among existing algorithmic quality-control mechanisms on Wikipedia (bots, semi-automated tools, ORES)?
 * Q2: Edit filters are a classical rule-based system. Why are they still active today when more sophisticated ML approaches exist?
 * Q3: Which type of tasks do filters take over?
-* Q4: How have these tasks evolved over time (are they changes in the type, number, etc.)?
+* Q4: How have these tasks evolved over time (are there changes in the type, number, etc.)?
 
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