Improve regular expressions

This change will ensure that the first `sed` command that removes the
`kargs` key completely will also remove the following
`match-architectures` key if the key exists. Also, the second `sed`
command that just removes an item from the list if the list contains
multiple items has been adjusted to correctly remove commans between
the items.

Credit to Matus Marhefka 👍

shared/templates/grub2_bootloader_argument_absent/bash.template

@@ -4,8 +4,8 @@
    Product-specific categorization should be synced across all template content types
 -#}}
 if {{{ bash_bootc_build() }}} ; then
-    sed -i -E "/kargs\s*=\s*\[\s*\"{{{ ARG_NAME }}}=[^\"]*\"\s*]/d" "$KARGS_DIR/*.toml"
-    sed -i -E "s/^(\s*kargs\s*=\s*\[.*)\"{{{ ARG_NAME }}}=[^\"]*\"(.*]\s*)/\1\2/" "$KARGS_DIR/*.toml"
+    sed -i -E "/kargs\s*=\s*\[\s*\"{{{ ARG_NAME }}}=[^\"]*\"\s*]/{:a;N;/^\n$/ba;N;/match-architectures.*/d;}" "$KARGS_DIR/*.toml"
+    sed -i -E -e "s/^(\s*kargs\s*=\s*\[.*)\"{{{ ARG_NAME }}}=[^\"]*\"[,[:space:]]*(.*]\s*)/\1\2/" -e "s/^(\s*kargs.*),\s*\]$/\1\]/" "$KARGS_DIR/*.toml"
 else
 {{{ grub2_bootloader_argument_absent_remediation(ARG_NAME) }}}
 fi