Add delete method for IndexLens on strings (fixes #199) #677

Job	Run time
Julia lts - ubuntu-latest - - push	2m 0s
Julia 1 - windows-latest - - push	4m 51s
Julia lts - windows-latest - - push	2m 33s
Julia pre - ubuntu-latest - - push	3m 49s
Julia 1 - macOS-latest - - push	3m 33s
Julia pre - windows-latest - - push	4m 35s
Julia pre - macOS-latest - - push	2m 29s
Julia lts - macOS-latest - - push	1m 47s
Documentation	1m 26s
Julia 1 - ubuntu-latest - - push	4m 23s
	31m 26s

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