Fix default for max-positional-args (#9838)

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## Summary
`max-positional-args` defaults to `max-args` if it's not specified and
the default to `max-args` is 5, so saying that the default is 3 is
definitely wrong. Ideally, we wouldn't specify a default at all for this
config option, but I don't think that's possible?

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## Test Plan

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Not sure.

crates/ruff_workspace/src/options.rs

@@ -2756,7 +2756,7 @@ pub struct PylintOptions {
     ///
     /// If not specified, defaults to the value of `max-args`.
     #[option(
-        default = r"3",
+        default = r"5", // Needs to be in sync with default of `max-args`.
         value_type = "int",
         example = r"max-positional-args = 3"
     )]