WASHINGTON — California Sen. Dianne Feinstein returned to the Senate on Wednesday after a two-and-a-half-month absence due to illness, giving majority Democrats a much-needed final vote as they seek to confirm President Joe Biden’s nominees and raise the nation’s debt ceiling in the coming weeks.Looking noticeably thinner and frail, Feinstein is using a wheelchair to get around the Capitol as she continues to recover from a case of shingles. She missed the Senate’s first votes on Wednesday morning …