[llvm] [llvm-readobj][NFC] Don't use startLine in a middle of a line in ObjDumper. (PR #102071)

[Jacek Caban via llvm-commits]

cjacek wrote:

Yes, it's checked by `file-headers.test` tests (a few of them, for various formats) and `hex-dump.test`. I verified that they fail if I intentionally "break" the code to output an additional space. I will also make tests in #102245 more strict, to make sure that indentation works as expected.

https://github.com/llvm/llvm-project/pull/102071