Remove unused index in DMST module #310

Job	Run time
build-all-debug	7m 5s
build-all-debug-single	3m 28s
build-postlib-release	11m 26s
build-drivers-release	5m 16s
build-test-uadriver-debug	1m 48s
rtest-module-drivers	4m 28s
rtest-modules-debug	11m 11s
build-fastfarm-release	12m 44s
build-interfaces-release	4m 47s
build-openfast-release	5m 52s
rtest-interfaces	3m 55s
rtest-OF-5MW_Land_AeroMap	1m 12s
rtest-OF-5MW_OC4Jckt_DLL_WTurb_WavesIrr_MGrowth	2m 30s
rtest-OF	15m 32s
rtest-OF-5MW_OC3Mnpl_DLL_WTurb_WavesIrr	1m 57s
rtest-OF-5MW_Land_BD_DLL_WTurb	2m 15s
rtest-OF-5MW_OC3Trpd_DLL_WSt_WavesReg	4m 46s
rtest-OF-5MW_OC4Semi_WSt_WavesWN	1m 29s
rtest-OF-simulink	11m 46s
rtest-OF-linearization	4m 59s
rtest-FF	2m 16s
	2h 0m 42s

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