[roll] Roll llvm-project/libc [libc][test] Remove more unused nan variables (#155925)

These are redefined/shadowed by the if constexpr (FPBits::FRACTION_LEN -
1 >= 5) case below.

Added by llvm/llvm-project#155569. I missed
these ones in #155894.

GitOrigin-RevId: 3ea7956fd326defab6d1b9a97d9bbd80b5ca3505
Original-Revision: b40c9b8d009430302e7d1917a4e37b9120fe982b

Rolled-Repo: https://llvm.googlesource.com/llvm-project/libc
Rolled-Commits: be3c2eaf490158..b40c9b8d009430
Roller-URL: https://cr-buildbucket.appspot.com/build/8705226799329368289
CQ-Do-Not-Cancel-Tryjobs: true
Cq-Include-Trybots: luci.turquoise.global.try:run-postsubmit-tryjobs
Change-Id: I138c8e2d8835555b5d99c05d32a284c2cded00de
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1356900
Commit-Queue: GI Roller <[email protected]>

Author: Jordan Rupprecht

manifests/third_party/all

@@ -295,7 +295,7 @@
     <project name="llvm-project/libc"
              path="third_party/llvm-libc/src"
              remote="https://llvm.googlesource.com/llvm-project/libc"
-             revision="be3c2eaf49015864e4a1a7b9e8c707c78022c967"/>
+             revision="b40c9b8d009430302e7d1917a4e37b9120fe982b"/>
     <project name="third_party/luci-go"
              path="third_party/luci-go"
              revision="fd977bf9e01d199a529f28af6dc10fe0fa35d9e7"