Typo Correction in planck/rev7 readme.md (qmk#21194)

Corrected typo explaining encoder requirements.

keyboards/planck/rev7/readme.md

@@ -14,7 +14,7 @@ See the [build environment setup](https://docs.qmk.fm/#/getting_started_build_to
 
 ## Encoders
 
-Encoders much have matching pulse & detent resolutions (e.g. 24/24) for the scanning to work properly. Multiple encoders can be used at the same time, and are zero-indexed (compared to being one-indexed on the PCB's silkscreen) in the `encoder_update_user(index, clockwise)` function:
+Encoders must have matching pulse & detent resolutions (e.g. 24/24) for the scanning to work properly. Multiple encoders can be used at the same time, and are zero-indexed (compared to being one-indexed on the PCB's silkscreen) in the `encoder_update_user(index, clockwise)` function:
 
 ```
 ,-----------------------------------------------------------------------------------.
@@ -28,4 +28,4 @@ Encoders much have matching pulse & detent resolutions (e.g. 24/24) for the scan
 `-----------------------------------------------------------------------------------'
 ```
 
-If an encoder has a switch built-in, it's connected to the key at that location. On the default keymap, each encoder will play its own rising/falling tone sequence when rotated, and will reset the pitch after one second of inactivity.
+If an encoder has a switch built-in, it's connected to the key at that location. On the default keymap, each encoder will play its own rising/falling tone sequence when rotated, and will reset the pitch after one second of inactivity.