Implement change discussed during PR review to the developer upgrade guide

Author: rodrigoprimo

wiki/Version-4.0-Developer-Upgrade-Guide.md

@@ -537,7 +537,7 @@ The Ruleset class now respects sniff selection via `--sniffs=...`, even when in
 
 If your own test framework contained workarounds to get round the previous restriction, it should now be safe to remove those workarounds and to use the `--sniffs=...` argument when initiating the `Config` class.
 
-Typically, these types of workarounds can be found by searching for calls to the `Ruleset::registerSniffs()` method.
+Typically, these type of workarounds can be found by searching for calls to the `Ruleset::registerSniffs()` method.
 
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