explicitly disable -Zmir-include-spans in mir-opt tests

This will override the NLL default of true, and keep the blessed dumps
easier to work with.

Author: lqd

src/tools/compiletest/src/runtest.rs

@@ -2175,6 +2175,7 @@ impl<'test> TestCx<'test> {
                     "-Zvalidate-mir",
                     "-Zlint-mir",
                     "-Zdump-mir-exclude-pass-number",
+                    "-Zmir-include-spans=false",
                     "--crate-type=rlib",
                 ]);
                 if let Some(pass) = &self.props.mir_unit_test {