[llvm] [QualGroup][docs] Update meeting schedule and link for slides (PR #169458)

[via llvm-commits]

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uwendi wrote:

Very minimal suggestion here.

Replace `Note: that the naming convention for these slides is YYYYMM_llvm_qual_wg.`
by `Note that the naming convention for these slides is *YYYYMM*_llvm_qual_wg.`

https://github.com/llvm/llvm-project/pull/169458