servo: Merge #11352 - Fixed colspan not including cell spacing (from cbrewster:colspan_spacing); r=pcwalton

Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data:
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy --faster` does not report any errors
- [X] These changes fix #11351 (github issue number if applicable).

Either:
- [X] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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Source-Repo: https://github.com/servo/servo
Source-Revision: 7b467ee52d59d1d2f078948acc9e4d188eac7338

servo/components/layout/table_row.rs

@@ -357,7 +357,7 @@ impl Flow for TableRowFlow {
                         None => break,
                     };
                 column_computed_inline_size.size = column_computed_inline_size.size +
-                    extra_column_computed_inline_size.size;
+                    extra_column_computed_inline_size.size + self.spacing.horizontal;
             }
 
             computed_inline_size_for_cells.push(column_computed_inline_size)