A House committee Thursday narrowly approved the proposed sale of 40 F- 6 jet fighters to Pakistan, overriding liberal opposition and handling Presidnet Reagan another major foreign policy victory. The House Foreign Affairs Committee voted 13 to to 13 defeat a resolution to block the $1.1 billion sale. A tie vote is enough to defeat such a proposal. The Senate Foreign Relations Committee defeated a similiar resolution Tuesday. Together the two votes signal that the sale, which the Reagan administration says would help Pakistan protect itself against the Soviet Union, is likely to go ahead.