lib/sources: remove 2 usages of toString on a path which will be read using fileContents

It gives a warning on the lazy-trees branch of Nix
(NixOS/nix#6530)

"warning: applying 'toString' to path '...' and then accessing it is deprecated, at '...'"

'else toString (/. + "${base}/${path}");' at line 183 may still cause a warning but i don't know how
to reach that codepath and test so im leaving it untouched

changing it to 'else /. + "${base}/${path}";'
caused this error
```
error: a string that refers to a store path cannot be appended to a path

       at /home/systems/nixpkgs/lib/sources.nix:183:20:

          182|               then path
          183|               else /. + "${base}/${path}";
             |                    ^
          184|         in if pathIsRegularFile path
```

0 files changed, 0 insertions, 0 deletions