nixos/doc: fix package extension links

The package extension links point to a blank page, because the package
query is set as a path instead of a query parameter.

Changed files
+2 -2
nixos
doc
manual
+2 -2
nixos/doc/manual/configuration/customizing-packages.section.md
···
::: {.note}
For example, many packages come with extensions one might add.
Examples include:
-
- [`passExtensions.pass-otp`](https://search.nixos.org/packages/query=passExtensions.pass-otp)
-
- [`python310Packages.requests`](https://search.nixos.org/packages/query=python310Packages.requests)
You can use them like this:
```nix
···
::: {.note}
For example, many packages come with extensions one might add.
Examples include:
+
- [`passExtensions.pass-otp`](https://search.nixos.org/packages?query=passExtensions.pass-otp)
+
- [`python312Packages.requests`](https://search.nixos.org/packages?query=python312Packages.requests)
You can use them like this:
```nix