fix categories

Author: ivmarkov

Cargo.toml

@@ -8,7 +8,7 @@ description = "Async I/O fork for embedded systems"
 license = "Apache-2.0 OR MIT"
 repository = "https://github.com/ivmarkov/async-io-mini"
 keywords = ["select", "ESP-IDF"]
-categories = ["asynchronous", "network-programming", "MCU", "embedded"]
+categories = ["asynchronous", "network-programming", "embedded"]
 exclude = ["/.*"]
 
 [features]