Fix # nolint flag linter exclusion syntax

[joshwlambert]

This PR fixes the syntax of # nolint flags in the code that specify a specific linter to exclude for that line or chunk of lines. Previously, the linter wanting to be excluded was specified but not recognised by {lintr} due to not using the # nolint: linter_name, linter2_name. syntax, specifically not using a colon or full stop. See https://lintr.r-lib.org/reference/exclude.html.

The specific linter being excluded has been removed from # nolint end statements as it is not required, see https://lintr.r-lib.org/articles/lintr.html#excluding-multiple-lines-of-codes.

Lines that had a # nolint flag that caused the line to exceed 80 characters have been converted into # nolint start and # nolint end statements, to avoid having to also specify the line_length_linter, making that line of code exceedingly long.

The vignettes that include # nolint flags in code chunks have also been updated to only echo the functional code and user-intended comments.