You have to delete the comma between [TechWriter] = 'Yes' and the WHERE clause:
UPDATE [RevsionRecords] SET [VPoME] = 'Yes', [DoTSE] = '', [DoM] = 'Yes', [CI] = '', [MoMC] = '', [MoMP] = '', [MoRD] = '', [FAA] = '', [TechWriter] = 'Yes' WHERE [RevisionNum] = '2015-100')