fix: correct grammar for hardware versions

Co-authored-by: sourcery-ai[bot] <58596630+sourcery-ai[bot]@users.noreply.github.com>

Author: iam-pradeepkumar

README.md

@@ -1,6 +1,6 @@
 # 🔬 PSLab Firmware
 
-This repository contains firmware for the [Pocket Science Lab (PSLab)](https://pslab.io) open hardware platform. Hardware version 5 and 6 are supported.
+This repository contains firmware for the [Pocket Science Lab (PSLab)](https://pslab.io) open hardware platform. Hardware versions 5 and 6 are supported.
 
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