The 1906 LDS edition accidentally replaced the present-tense covenanteth with the past-tense covenanted. Since this edition never served as a copy-text for any subsequent LDS edition, this typo has never continued in the text. God’s willingness to covenant with mankind holds throughout time; thus the use of present tense is appropriate here.
Summary: Maintain the present-tense covenanteth in 2 Nephi 30:2.