[esp32_rmt_led_strip] Fix clang-tidy signed/unsigned comparison warning (#11033)

esphome/components/esp32_rmt_led_strip/led_strip.cpp

@@ -35,7 +35,7 @@ static size_t IRAM_ATTR HOT encoder_callback(const void *data, size_t size, size
     if (symbols_free < RMT_SYMBOLS_PER_BYTE) {
       return 0;
     }
-    for (int32_t i = 0; i < RMT_SYMBOLS_PER_BYTE; i++) {
+    for (size_t i = 0; i < RMT_SYMBOLS_PER_BYTE; i++) {
       if (bytes[index] & (1 << (7 - i))) {
         symbols[i] = params->bit1;
       } else {