Upgrade to Rust 1.86 and bump MSRV to 1.84 (#17171)

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## Summary

I decided to disable the new
[`needless_continue`](https://rust-lang.github.io/rust-clippy/master/index.html#needless_continue)
rule because I often found the explicit `continue` more readable over an
empty block or having to invert the condition of an other branch.


## Test Plan

`cargo test`

---------

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>

crates/ruff_python_parser/src/semantic_errors.rs

@@ -449,7 +449,7 @@ impl SemanticSyntaxChecker {
                             }
                         }
                         _ => {}
-                    };
+                    }
                 }
 
                 // PLE0118
@@ -781,7 +781,7 @@ impl Visitor<'_> for ReboundComprehensionVisitor<'_> {
                 }) {
                     self.rebound_variables.push(*range);
                 }
-            };
+            }
         }
         walk_expr(self, expr);
     }