bash: remove force nix shell bit in favor of another solution

(also, this aparantly made it so the env variables didn't make it to
zsh, so `nix-shell -p` commands effectively didn't do anything)

.bashrc

@@ -17,11 +17,6 @@ export SHELL_CONFIG_DIR="${SHELL_CONFIG_DIR:-"${XDG_CONFIG_HOME:-"$HOME/.config"
 # Source standard shell configuration
 [ -f "$SHELL_CONFIG_DIR/shrc" ] && source "$SHELL_CONFIG_DIR/shrc"
 
-# if in nix shell, run zsh instead of bash - not sure if there's a better way to do this
-if ! "${FORCE_BASH:-false}" && [ -n "$IN_NIX_SHELL" ]; then
-   SHELL="/etc/profiles/per-user/$USER/bin/zsh" exec zsh
-fi
-
 ### Manjaro default bashrc >>>
 colors() {
 	local fgc bgc vals seq0