Typo in hyperlink in language reference page for variables

Both links to the scope documentation page found in [the "Variables" language reference page](https://www.arduino.cc/en/Reference/VariableDeclaration) redirect towards an URL that has a typo in it, which loads a blank page.

Both links are present in the two "Variable scope" sections, the links point towards a redirection page (https://www.arduino.cc/en/Reference/Scope) which itself redirects to [https://www.arduino.cc/reference/en/language/variables/variable-scope--qualifiers/scope/](https://www.arduino.cc/reference/en/language/variables/variable-scope--qualifiers/scope/), notice the two hyphens at the end of the address, whereas the actual page has a single hyphen.

Removing the hyphen manually fixes the issue and loads the intended page.