Rename doc/manual{src -> source}

This is needed to avoid this
https://github.com/mesonbuild/meson/issues/13774 when we go back to
making our subproject directory `src`.

doc/manual/src/command-ref/nix-store.md

@@ -1,47 +0,0 @@
-# Name
-
-`nix-store` - manipulate or query the Nix store
-
-# Synopsis
-
-`nix-store` *operation* [*options…*] [*arguments…*]
-  [`--option` *name* *value*]
-  [`--add-root` *path*]
-
-# Description
-
-The command `nix-store` performs primitive operations on the Nix store.
-You generally do not need to run this command manually.
-
-`nix-store` takes exactly one *operation* flag which indicates the subcommand to be performed. The following operations are available:
-
-- [`--realise`](./nix-store/realise.md)
-- [`--serve`](./nix-store/serve.md)
-- [`--gc`](./nix-store/gc.md)
-- [`--delete`](./nix-store/delete.md)
-- [`--query`](./nix-store/query.md)
-- [`--add`](./nix-store/add.md)
-- [`--add-fixed`](./nix-store/add-fixed.md)
-- [`--verify`](./nix-store/verify.md)
-- [`--verify-path`](./nix-store/verify-path.md)
-- [`--repair-path`](./nix-store/repair-path.md)
-- [`--dump`](./nix-store/dump.md)
-- [`--restore`](./nix-store/restore.md)
-- [`--export`](./nix-store/export.md)
-- [`--import`](./nix-store/import.md)
-- [`--optimise`](./nix-store/optimise.md)
-- [`--read-log`](./nix-store/read-log.md)
-- [`--dump-db`](./nix-store/dump-db.md)
-- [`--load-db`](./nix-store/load-db.md)
-- [`--print-env`](./nix-store/print-env.md)
-- [`--generate-binary-cache-key`](./nix-store/generate-binary-cache-key.md)
-
-These pages can be viewed offline:
-
-- `man nix-store-<operation>`.
-
-  Example: `man nix-store-realise`
-
-- `nix-store --help --<operation>`
-
-  Example: `nix-store --help --realise`