test: Subtract code_offset from width for ui_testing

Author: Muscraft

tests/ui/option_env_unwrap.stderr

@@ -19,7 +19,7 @@ LL |     let _ = option_env!("PATH").expect("environment variable PATH isn't set
 error: this will panic at run-time if the environment variable doesn't exist at compile-time
   --> tests/ui/option_env_unwrap.rs:14:13
    |
-LL |     let _ = option_env!("__Y__do_not_use").unwrap(); // This test only works if you don't have a __Y__do_not_use env variable in your env...
+LL |     let _ = option_env!("__Y__do_not_use").unwrap(); // This test only works if you don't have a __Y__do_not_use env variable in you...
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: consider using the `env!` macro instead

tests/ui/too_long_first_doc_paragraph.stderr

@@ -42,7 +42,7 @@ LL | | /// gravida non lacinia at, rhoncus eu lacus.
 error: first doc comment paragraph is too long
   --> tests/ui/too_long_first_doc_paragraph.rs:65:1
    |
-LL | / /// Some function. This doc-string paragraph is too long. Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lore...
+LL | / /// Some function. This doc-string paragraph is too long. Lorem Ipsum is simply dummy text of the printing and typesetting industr...
 LL | |
 LL | | ///
 LL | | /// Here's a second paragraph. It would be preferable to put the details here.