Fix a typo in the header generation message.
Before:
Generating header from
/home/vscode/llvm-project/llvm/../libc/newhdrgen/yaml/ctype.yaml and
/home/vscode/llvm-project/libc/include/ctype.h.def
After:
Generating header ctype.h from
/home/vscode/llvm-project/llvm/../libc/newhdrgen/yaml/ctype.yaml and
/home/vscode/llvm-project/libc/include/ctype.h.def