[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/0007-Explicitly-use-std.patch

@@ -76,6 +76,3 @@ index 18beb3878067..081b699adee3 100644
  
    SmallVector<std::string_view, 4> Expected = {"A", "B", "C", "D"};
    EXPECT_EQ(Expected, Keys);
--- 
-2.20.1.windows.1
-