README.md: Make CodeQL badge clickable
README.md: Make CodeQL badge clickable

This is a better fix for issue #3958.
amitdo/tesseract,tesseract-ocr/tesseract,amitdo/tesseract,amitdo/tesseract,tesseract-ocr/tesseract,tesseract-ocr/tesseract,amitdo/tesseract,tesseract-ocr/tesseract,tesseract-ocr/tesseract,amitdo/tesseract