put valid category for ESP_I2S

ESP_I2S was categorized as "Sound", which is not a valid category.  "Signal Input/Output" is a valid category.

see
https://arduino.github.io/arduino-cli/1.2/library-specification/#libraryproperties-file-format
for a list of valid categories (search for "category" on that page).

current valid categories are:


   - Display
   - Communication
   - Signal Input/Output
   - Sensors
   - Device Control
   - Timing
   - Data Storage
   - Data Processing
   - Other

Author: ozzloy

libraries/ESP_I2S/library.properties

@@ -4,6 +4,6 @@ author=me-no-dev
 maintainer=me-no-dev
 sentence=Library for ESP I2S communication
 paragraph=Supports ESP32 Arduino platforms.
-category=Sound
+category=Signal Input/Output
 url=https://github.com/espressif/arduino-esp32/
 architectures=esp32