style: make MicrobitMore completion instruction bold and red

- Add .important-instruction style to connection-modal.css
- Apply importantInstruction style to MicrobitMore tilt instruction in UpdatePeripheralStep

Co-Authored-By: Gemini <noreply@google.com>

Author: takaokouji

src/components/connection-modal/connection-modal.css

@@ -446,3 +446,8 @@
     height: 60%;
     width: inherit;
 }
+
+.important-instruction {
+    font-weight: bold;
+    color: $red-primary;
+}

src/components/connection-modal/update-peripheral-step.jsx

@@ -146,7 +146,7 @@ class UpdatePeripheralStep extends React.Component {
                             id="gui.connection.updatePeripheral.microbitMoreUpdateSuccessful"
                         />
                         <FormattedMessage
-                            className={styles.centeredRow}
+                            className={classNames(styles.centeredRow, styles.importantInstruction)}
                             defaultMessage="Tilt your micro:bit to light up all 25 LEDs to complete."
                             description="Instructions to tilt the micro:bit to complete the update process"
                             id="gui.connection.updatePeripheral.microbitMoreTiltToLightUp"