Fix typos in CardInfo example

examples/CardInfo/CardInfo.ino

   // since we're just testing if the card is working!
   if (!card.init(SPI_HALF_SPEED, chipSelect)) {
     Serial.println("initialization failed. Things to check:");
-    Serial.println("* is a card is inserted?");
-    Serial.println("* Is your wiring correct?");
+    Serial.println("* is a card inserted?");
+    Serial.println("* is your wiring correct?");
     Serial.println("* did you change the chipSelect pin to match your shield or module?");
     return;
   } else {