Use "command -v" instead of "which" in bash scripts

shellcheck recently added SC2330 checking for this. "which" is non-standard, and
not guaranteed by POSIX to have a meaningful exit status, while "command -v" is
specified by POSIX: https://stackoverflow.com/q/592620

misc/userscripts/open_download

@@ -52,7 +52,7 @@ die() {
 if ! [ -d "$DOWNLOAD_DIR" ] ; then
     die "Download directory »$DOWNLOAD_DIR« not found!"
 fi
-if ! which "${ROFI_CMD}" > /dev/null ; then
+if ! command -v "${ROFI_CMD}" > /dev/null ; then
     die "Rofi command »${ROFI_CMD}« not found in PATH!"
 fi
 

misc/userscripts/password_fill

@@ -220,7 +220,7 @@ user_pattern='^(user|username|login): '
 GPG_OPTS=( "--quiet" "--yes" "--compress-algo=none" "--no-encrypt-to" )
 GPG="gpg"
 export GPG_TTY="${GPG_TTY:-$(tty 2>/dev/null)}"
-which gpg2 &>/dev/null && GPG="gpg2"
+command -v gpg2 &>/dev/null && GPG="gpg2"
 [[ -n $GPG_AGENT_INFO || $GPG == "gpg2" ]] && GPG_OPTS+=( "--batch" "--use-agent" )
 
 pass_backend() {