Fix trailing spaces in scheme / pathname / search setters

[lucacasonato]

Fixes https://github.com/servo/rust-url/issues/847

Related #816

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (93b8e2f) 82.43% compared to head (4d3e9e9) 82.43%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #848 +/- ## ======================================= Coverage 82.43% 82.43% ======================================= Files 20 20 Lines 3348 3348 ======================================= Hits 2760 2760 Misses 588 588 ``` | [Impacted Files](https://app.codecov.io/gh/servo/rust-url/pull/848?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=servo) | Coverage Δ | | |---|---|---| | [url/src/lib.rs](https://app.codecov.io/gh/servo/rust-url/pull/848?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=servo#diff-dXJsL3NyYy9saWIucnM=) | `76.03% <100.00%> (+0.06%)` | :arrow_up: | | [url/src/parser.rs](https://app.codecov.io/gh/servo/rust-url/pull/848?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=servo#diff-dXJsL3NyYy9wYXJzZXIucnM=) | `80.78% <100.00%> (-0.05%)` | :arrow_down: | | [url/src/path\_segments.rs](https://app.codecov.io/gh/servo/rust-url/pull/848?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=servo#diff-dXJsL3NyYy9wYXRoX3NlZ21lbnRzLnJz) | `80.00% <100.00%> (ø)` | | | [url/src/quirks.rs](https://app.codecov.io/gh/servo/rust-url/pull/848?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=servo#diff-dXJsL3NyYy9xdWlya3MucnM=) | `96.72% <100.00%> (ø)` | |

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