[lldb] [llvm] [lldb][DeclVendor] Remove ClangDeclVendor (PR #164380)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-ppc64le-linux-multistage` running on `ppc64le-clang-multistage-test` while building `lldb,llvm` at step 11 "ninja check 2".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/76/builds/13267

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 11 (ninja check 2) failure: 1200 seconds without output running [b'ninja', b'check-all'], attempting to kill
...
PASS: SanitizerCommon-lsan-powerpc64le-Linux :: Linux/signal_segv_handler.cpp (103131 of 103141)
PASS: SanitizerCommon-msan-powerpc64le-Linux :: Linux/signal_segv_handler.cpp (103132 of 103141)
PASS: SanitizerCommon-tsan-powerpc64le-Linux :: Linux/signal_segv_handler.cpp (103133 of 103141)
PASS: LLVM :: MC/Mips/elf_eflags.s (103134 of 103141)
PASS: LLVM :: Object/macho-invalid.test (103135 of 103141)
PASS: mlgo-utils :: corpus/extract_ir_script.test (103136 of 103141)
PASS: lit :: shtest-define.py (103137 of 103141)
PASS: LLVM :: tools/llvm-readobj/ELF/file-header-machine-types.test (103138 of 103141)
PASS: LLVM :: tools/llvm-readobj/ELF/AMDGPU/elf-headers.test (103139 of 103141)
PASS: LLVM :: CodeGen/X86/cpus-intel.ll (103140 of 103141)
command timed out: 1200 seconds without output running [b'ninja', b'check-all'], attempting to kill
process killed by signal 9
program finished with exit code -1
elapsedTime=4669.959253

```

</details>

https://github.com/llvm/llvm-project/pull/164380