add skip test for qtpy (missing A4), and fix unused warnings

.github/workflows/githubci.yml

@@ -7,11 +7,11 @@ jobs:
     runs-on: ubuntu-latest
     
     steps:
-    - uses: actions/setup-python@v1
+    - uses: actions/setup-python@v4
       with:
         python-version: '3.x'
-    - uses: actions/checkout@v2
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
+    - uses: actions/checkout@v3
       with:
          repository: adafruit/ci-arduino
          path: ci

Adafruit_MFRC630.cpp

@@ -795,6 +795,7 @@ uint16_t Adafruit_MFRC630::iso14443aCommand(enum iso14443_cmd cmd) {
  * https://www.nxp.com/docs/en/application-note/AN10833.pdf
  */
 uint8_t Adafruit_MFRC630::iso14443aSelect(uint8_t *uid, uint8_t *sak) {
+  (void)sak;
   DEBUG_TIMESTAMP();
   DEBUG_PRINTLN(F("Selecting an ISO14443A tag"));