Broken Google Slides template link

[mx-psi]

Our README has a broken link since at least this week to a Google Slides template:

community/README.md

Line 104 in d3c79d5

repository](https://github.com/cncf/artwork/tree/master/projects/opentelemetry). In addition, a [Google Slides template](https://docs.google.com/presentation/d/1Neab3OZ3c-m5kOE37iZXEVpK4Pjj6xGTJEUuUzLQJvk/edit?usp=sharing) is also available.

This was added on #481 as part of resolving #347.

@flands you seem to be the owner/creator of this template, could you look into it? Ideally we would move this file onto an OpenTelemetry-owned Google account.

[alolita]

The slides template link on README is broken. @flands Please remove the broken link so that other PRs can be merged. Ty!

[mtwo]

Our splunk.com Google accounts were deleted a few weeks ago, however all of the content was moved to Office 365. @flands should be able to recover the content into a new Google Slides file once he's back from vacation.