[ELF][AArch64] Fix copy/paste error in llvm_unreachable message

Fixes: e1979aed0a15 ("Implement gd to ie relaxation for aarch64.")
diff --git a/lld/ELF/Arch/AArch64.cpp b/lld/ELF/Arch/AArch64.cpp
index 2a97df4..b0dc797 100644
--- a/lld/ELF/Arch/AArch64.cpp
+++ b/lld/ELF/Arch/AArch64.cpp
@@ -762,7 +762,7 @@
     relocateNoSym(loc, R_AARCH64_TLSIE_LD64_GOTTPREL_LO12_NC, val);
     break;
   default:
-    llvm_unreachable("unsupported relocation for TLS GD to LE relaxation");
+    llvm_unreachable("unsupported relocation for TLS GD to IE relaxation");
   }
 }