[roll] Roll llvm-project/libc [libc][docs] disable pthreads docs (#123824)

Having a target named pthreads is breaking when multiple runtimes are enabled.
Disable this target for now so that the builds go back to green (and sites get
updated).

Link: llvm/llvm-zorg#359 (comment)
Link: #122006
Link: #122497
Link: #123821
GitOrigin-RevId: 6ac1fb4fd88250e38b9c0c7d9af792cb82c2da05
Original-Revision: e58422d81dea98c3acd2b044916d905ec13ca781
Change-Id: I82507d0c03183997f13ca002d5f97e892f5e8f78

Author: Nick Desaulniers

third_party/flower

@@ -369,7 +369,7 @@
              gitsubmoduleof="fuchsia"
              path="third_party/llvm-libc/src"
              remote="https://llvm.googlesource.com/llvm-project/libc"
-             revision="2423bce213c0f89ff3d3855f4429c490a4b711a1"/>
+             revision="e58422d81dea98c3acd2b044916d905ec13ca781"/>
     <project name="third_party/lz4"
              gitsubmoduleof="fuchsia"
              path="third_party/lz4"