By Peter Nicholls WINDSOR, England (Reuters) -Queen Elizabeth tested positive for COVID-19 on Sunday, sharpening concerns about the health of the world’s longest-reigning monarch two weeks after she marked 70 years on the British throne. The 95-year-old queen, who has been fully vaccinated against coronavirus, quipped just four days ago to Palace staff that she could not move much, and she spent a night in hospital last October for an unspecified ailment. “The Queen has today tested positive for COVID,” the Palace said. “Her Majesty is experiencing mild cold like symptoms but expects to contin…