Remove `MatrixClient.initLegacyCrypto` #10743

Job	Run time
JSDoc Checker	28s
Analyse Dead Code	19s
ESLint	41s
Node.js example	29s
Typescript Syntax Check	27s
Workflow Lint	14s
Downstream tsc element-web	0s
Downstream Typescript Syntax Check	1s
	2m 39s

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