Fix 'occured' -> 'occurred' in user-visible 'parsing error' message

[SAY-5]

Fix 2 instances of occured → occurred:

• arduino-core/src/cc/arduino/contributions/packages/ContributionsIndexer.java line 118: The actual error source (System.err.println)
• arduino-core/src/processing/app/i18n/Resources_en.po lines 2007-2008: English i18n msgstr matches the source

The message 'Skipping contributed index file {0}, parsing error occured:' is user-visible in the Arduino IDE when parsing fails. Only the English source/translation is updated here — other locales regenerate from the source.

String-literal-only change.

[CLAassistant]

All committers have signed the CLA.

[SAY-5]

Closing — typo-only PR. Multiple maintainers across the OSS ecosystem have flagged my recent typo-sweep PRs as AI-generated spam (notably hashicorp/nomad#27855, hashicorp/hcl#794, argo-cd reviewers). I should have caught this pattern sooner. Apologies for the noise.

[per1234]

Thanks for taking the time to submit a pull request @SAY-5! Speaking for the repositories I maintain, fixes for typos are very welcome.

The problem with this specific pull request is that the Arduino IDE 1.x project hosted in this repository is no longer actively maintained:

Arduino/README.md

Line 5 in a0df6e0

**Important Notice**: This repository contains the legacy Arduino IDE 1.x, which is no longer in active development. For the latest features and updates, please visit the [Arduino IDE 2.x](https://github.com/arduino/arduino-ide) repository. If you encounter issues related to the newer IDE, please report them there.

so it is questionable whether the responsible parties would ever make the time to review and merge your PR. Furthermore, your fix would likely not end up ever being shipped to users via a new release.

However, feel free to submit PRs for typos to any of the actively maintained repositories under the arduino or arduino-libraries GitHub organizations.

As for the use of AI or other automated systems, the key is that these tools be used responsibly. LLMs are prone to hallucinations, and even conventional spell check tools are prone to false positives (especially when used on a codebase). So it would not be appropriate to submit PRs for fixes that were identified by a machine without first performing careful human validation. However, I don't have any reason to think that you are operating in an irresponsible manner. Other than missing the notice in the readme (which is completely understandable), this pull request was completely reasonable and appears to be valid (I'm not familiar with this specific codebase and its infrastructure, so I can't be certain).

Personally, I feel that best practices for typo fixes would be to perform a survey of the entire repository and submit fixes all typos that are identified in a single PR. However, I understand that not everyone has the time available to take on that extra burden of work, so I'm also fine with a "drive by" fix of a single typo you happened to notice.

On a side note, I really like this tool for finding misspelled words in software projects:

https://github.com/codespell-project/codespell