treewide: get rid of invalid buildPhases argument

I don't know where this comes from (I accidentally did that as well
once), but some derivations seem to use `buildPhases` rather than
`phases` in their derivations.

This kills all improper usages as the lack of a `phases` argument
didn't break the build, so this can be safely removed.

pkgs/servers/tt-rss/default.nix

@@ -10,8 +10,6 @@ stdenv.mkDerivation rec {
     sha256 = "07ng21n4pva56cxnxkzd6vzs381zn67psqpm51ym5wnl644jqh08";
   };
 
-  buildPhases = ["unpackPhase" "installPhase"];
-
   installPhase = ''
     mkdir $out
     cp -ra * $out/