[compiler] Remove an obsolete comment

The NowIs operator doesn't exist anymore.

R=mslekova@chromium.org

Change-Id: Id081c7e0cf5b122a77598fc0b886a2d1c09c881f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3172767Reviewed-by: Maya Lekova <mslekova@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/main@{#76968}

src/compiler/types.h

@@ -72,10 +72,6 @@ namespace compiler {
 // existing assumptions or tests.
 // Consequently, do not normally use Equals for type tests, always use Is!
 //
-// The NowIs operator implements state-sensitive subtying, as described above.
-// Any compilation decision based on such temporary properties requires runtime
-// guarding!
-//
 //
 // PROPERTIES
 //