ref(markLine): Rename MarkLine factory to markLine to fix linting

[sentry]

This PR renames the MarkLine factory function to markLine in static/app/components/charts/components/markLine.tsx.

The previous naming convention used a capitalized identifier (MarkLine) for a plain factory function call, which violated the no-capitalized-function-calls linting rule. This rule reserves capitalized names for React components (used as JSX) or class constructors.

All import statements and call sites across the codebase that used MarkLine(...) have been updated to markLine(...). In some instances, local variables named markLine were renamed to markLineSeries to avoid shadowing the newly imported markLine function.

Legal Boilerplate

Look, I get it. The entity doing business as "Sentry" was incorporated in the State of Delaware in 2015 as Functional Software, Inc. and is gonna need some rights from me in order to utilize my contributions in this here PR. So here's the deal: I retain all rights, title and and interest in and to my contributions, and by keeping this boilerplate intact I confirm that Sentry can use, modify, copy, and redistribute my contributions, under Sentry's choice of terms.

Fixes CODING-CONVENTIONS-1TQ

[ryan953]

Closing as a duplicate — this same MarkLine -> markLine rename is consolidated in #121930, which now also references this issue's Sentry ticket so merging it will close it too.