bash: Let bash load completions lazily

As described in detail here: https://github.com/NixOS/nixpkgs/issues/32533
bash will load completion scripts in $p/share/bash-completion/completions/ on
startup instead of letting bash-completion do it's lazy loading. Bash startup
will then slow down (very noticeable when bash-completion is installed in a
profile).

This commit leaves loading of scripts in the hands of bash-completion,
improving startup time for everyone using `enableCompletion`.

Fixes #101

modules/programs/bash/default.nix

@@ -83,7 +83,7 @@ in
           nullglobStatus=$(shopt -p nullglob)
           shopt -s nullglob
           for p in $NIX_PROFILES; do
-            for m in "$p/etc/bash_completion.d/"* "$p/share/bash-completion/completions/"*; do
+            for m in "$p/etc/bash_completion.d/"*; do
               source $m
             done
           done