Fix "packages" typo in versioning.md (#6533)

Fix for a small typo: "these package" -> "these packages" (correct use
of plural)

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Author: C0Florent

src/content/tools/pub/versioning.md

@@ -197,7 +197,7 @@ evolution now. Let's see how they play together and what pub does.
 When you define your package, you list its
 [immediate dependencies][immediate-dep].
 These are packages that your package uses.
-For each of these package, you specify the range of versions your package allows.
+For each of these packages, you specify the range of versions your package allows.
 Each of those dependent packages might then have their own dependencies.
 These are called [transitive dependencies][transitive-dep].
 Pub traverses these and builds the entire dependency graph for your app.