[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/0019-Windows-Support.patch

@@ -218,6 +218,3 @@ index bcf13d828a5d..cddad9ca0660 100644
    // Read into Buffer until we hit EOF.
    for (;;) {
      Buffer.reserve(Buffer.size() + ChunkSize);
--- 
-2.20.1.windows.1
-