fix rustc_nonnull_optimization_guaranteed docs

[RalfJung]

As far as I can tell, even back when this was added it never enabled any optimizations. It just indicates that the FFI compat lint should accept those types for NPO.

[rustbot]

r? @nnethercote

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[rustbot]

Some changes occurred to the CTFE / Miri interpreter

cc @rust-lang/miri

[jieyouxu]

Thanks, r=me after reblessing the tests

[RalfJung]

@bors r=jieyouxu

[bors]

📌 Commit 8103505 has been approved by jieyouxu

It is now in the queue for this repository.

[bors]

⌛ Testing commit 8103505 with merge 4ae36d9...

[bors]

☀️ Test successful - checks-actions
Approved by: jieyouxu
Pushing 4ae36d9 to master...

[rust-timer]

Finished benchmarking commit (4ae36d9): comparison URL.

Overall result: ❌ regressions - no action needed

@rustbot label: -perf-regression

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	1.9%	[1.9%, 1.9%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

This benchmark run did not return any relevant results for this metric.

Cycles

Results (primary -1.7%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	0.5%	[0.5%, 0.5%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-3.8%	[-3.8%, -3.8%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-1.7%	[-3.8%, 0.5%]	2

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 769.195s -> 770.728s (0.20%)
Artifact size: 341.55 MiB -> 341.56 MiB (0.00%)