docs: use 'trezorctl firmware update'

Following #1258.

[no changelog]

docs/legacy/index.md

@@ -92,7 +92,7 @@ You can use `TREZOR_OLED_SCALE` environment variable to make emulator screen big
 2. Download it: `wget -O trezor.signed.bin https://data.trezor.io/firmware/1/trezor-1.9.4.bin`
 3. Use `trezorctl` dry-run mode to get the firmware fingerprint:
    ```sh
-   trezorctl firmware-update -n -f trezor.signed.bin
+   trezorctl firmware update -n -f trezor.signed.bin
    ```
 
 Step 3 should produce the same fingerprint like your local build (for the same version tag).
@@ -105,7 +105,7 @@ Build with `PRODUCTION=0` or you will get a hard fault on your device.
 
 Switch your device to bootloader mode, then execute:
 ```sh
-trezorctl firmware-update -f build/legacy/firmware/firmware.bin
+trezorctl firmware update -f build/legacy/firmware/firmware.bin
 ```
 
 ## Combining bootloader and firmware with various `PRODUCTION` settings, signed/unsigned

legacy/debug_signing/README.md

@@ -15,7 +15,7 @@
 By default the scripts uses the `[1, 2]` sigindices, you can modify `sig_indices`
 inside to have different order or different keys (1 <= index <= 3 )
 
-Update FW on T1 either via `trezorctl device firmware-update` or
+Update FW on T1 either via `trezorctl device firmware update` or
 `make flash_firmware_jlink`.
 
 ## Signing with the v2 method (called "new" for confusing historical reasons)

python/src/trezorlib/client.py

@@ -43,7 +43,7 @@ PASSPHRASE_TEST_PATH = parse_path("44h/1h/0h/0/0")
 
 OUTDATED_FIRMWARE_ERROR = """
 Your Trezor firmware is out of date. Update it with the following command:
-  trezorctl firmware-update
+  trezorctl firmware update
 Or visit https://suite.trezor.io/
 """.strip()