[llvm] [doc] Improve wording for "What is considered a security issue?" (PR #69436)

[Paul T Robinson via llvm-commits]

pogo59 wrote:

What I see is just reformatting, fixing an occasional typo, deleting the "FUTURE" remarks, and telling people that even though we say nothing is security-relevant, that shouldn't stop them from filing security issues. That all seems fine.

Sorry to have missed the Dev Meeting round table (had a conflict) and the last meeting (I've been ill). We have seemed to accept security reports as valid in a couple of areas, so "none" probably isn't really correct, but we should discuss that in a future meeting before updating this description.

https://github.com/llvm/llvm-project/pull/69436