mmgen-{txcreate,txdo}: change `--locktime` short opt from `-L` to `-l`

- this breaks compatibility, scripts may need to be adjusted

mmgen/main_split.py

@@ -48,7 +48,7 @@ opts_data = {
 -v, --verbose        Produce more verbose output
 -y, --yes            Answer 'yes' to prompts, suppress non-essential output
 -R, --rpc-host2=   h Host the other coin daemon is running on (default: none)
--L, --locktime=    t Lock time (block height or unix seconds)
+-l, --locktime=    t Lock time (block height or unix seconds)
                      (default: {bh})
 """,
 	'notes': f"""\n

mmgen/main_txcreate.py

@@ -49,7 +49,7 @@ opts_data = {
 -I, --inputs=      i  Specify transaction inputs (comma-separated list of
                       MMGen IDs or coin addresses).  Note that ALL unspent
                       outputs associated with each address will be included.
--L, --locktime=    t  Lock time (block height or unix seconds) (default: 0)
+-l, --locktime=    t  Lock time (block height or unix seconds) (default: 0)
 -m, --minconf=     n  Minimum number of confirmations required to spend
                       outputs (default: 1)
 -q, --quiet           Suppress warnings; overwrite files without prompting

mmgen/main_txdo.py

@@ -61,7 +61,7 @@ opts_data = {
 -k, --keys-from-file=f Provide additional keys for non-{pnm} addresses
 -K, --keygen-backend=n Use backend 'n' for public key generation.  Options
                        for {coin_id}: {kgs}
--L, --locktime=      t Lock time (block height or unix seconds) (default: 0)
+-l, --locktime=      t Lock time (block height or unix seconds) (default: 0)
 -m, --minconf=n        Minimum number of confirmations required to spend
                        outputs (default: 1)
 -M, --mmgen-keys-from-file=f Provide keys for {pnm} addresses in a key-