[upstream_utils] Remove git version from upstream patches (#4351)

This reduces commit noise when other git versions are used. The version
was removed by passing `--no-signature` to `git format-patch` which is
now documented in the readme.

upstream_utils/llvm_patches/0018-use-std-is_trivially_copy_constructible.patch

@@ -136,6 +136,3 @@ index 7b7d5d991f3f..72a2e84ad452 100644
  
  
  } // end namespace llvm
--- 
-2.20.1.windows.1
-