hw-spi: keep splat parameter notation unescaped in README

The previous commit's prettier pass escaped `*data` to `\*data` in
the SPI#write / SPI#transfer method signatures. The escape is
defensive (prettier avoids any standalone `*` to dodge italic
misparses) but unnecessary in these positions: GFM only treats `*`
as italic when paired with a closing `*`, which never happens in a
method signature. The unescaped form reads more naturally to Ruby
users.

Co-authored-by: Claude <noreply@anthropic.com>

mrbgems/hw-spi/README.md

@@ -50,7 +50,7 @@ spi = SPI.new(
 
 \*SPI3 availability depends on ESP32 variant.
 
-### SPI#write(\*data)
+### SPI#write(*data)
 
 Write data to the SPI bus. Data can be Integer, Array, or String.
 
@@ -68,7 +68,7 @@ data = spi.read(4)         # transmits 0x00 while reading
 data = spi.read(4, 0xFF)   # transmits 0xFF while reading
 ```
 
-### SPI#transfer(\*data, additional_read_bytes: 0)
+### SPI#transfer(*data, additional_read_bytes: 0)
 
 Full-duplex transfer. Sends data and returns received bytes.
 Use `additional_read_bytes:` to append zero-filled read bytes.