clang-ignore: remove unneeded file

openbmc-build-scripts by default uses git-ls-files and so does meson.
There is no reason to add untracked files into the .clang-ignore.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I1b5350a4050ec5b121ab425235f464a667d6bfe1
diff --git a/.clang-ignore b/.clang-ignore
deleted file mode 100644
index 36f17f2..0000000
--- a/.clang-ignore
+++ /dev/null
@@ -1 +0,0 @@
-./subprojects