Fix link in unstable book entry for Generators

Author: mattico

src/doc/unstable-book/src/language-features/generators.md

@@ -2,7 +2,7 @@
 
 The tracking issue for this feature is: [#43122]
 
-[#34511]: https://github.com/rust-lang/rust/issues/43122
+[#43122]: https://github.com/rust-lang/rust/issues/43122
 
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