FRANKFURT (Reuters) – A number of big investors on Monday filed to end their lawsuits against Allianz after a settlement was reached over their losses in a multibillion-dollar trading debacle at the German asset manager’s funds arm. The move marks an important milestone in the downfall of the $15 billion Structured Alpha funds, a saga that has dogged the German insurer and asset manager for two years. (Reporting by Tom Sims and Jonathan Stempel; Editing by Leslie Adler)