Revert "llvm: Update version from LLVM from 18.1.8 to 20.1.3"

This reverts commit 8720cb0.

It was just a test to get pahole building. It wasn’t the solution, and
not intended do be installed without updating the rest of the stack.

llvm.be0

@@ -1,9 +1,9 @@
 #!/usr/bin/env beesh
 
-# BEE_VERSION llvm-20.1.3-0
+# BEE_VERSION llvm-18.1.8-0
 
 #SRCURL[0]="https://github.com/llvm/llvm-project/releases/download/llvmorg-${PKGVERSION}/llvm-project-${PKGVERSION}.src.tar.xz"
-SRCURL[0]="https://beehive.molgen.mpg.de/b3741e8abc2b515159440da2b32898d8/llvm-project-20.1.3.src.tar.xz"
+SRCURL[0]="https://beehive.molgen.mpg.de/81cd0be5ae6f1ad8961746116d426a96/llvm-project-18.1.8.src.tar.xz"
 
 # PATCHURL+=()