[Doc] Fix GitHub capitalization in SEP guidelines (modelcontextprotocol#1048)

Follow-up to modelcontextprotocol/modelcontextprotocol#1045 (review).

Co-authored-by: David Soria Parra <[email protected]>

Author: koic

docs/community/sep-guidelines.mdx

@@ -44,8 +44,8 @@ Each SEP must have an **SEP author** -- someone who writes the SEP using the sty
 
 SEPs should be submitted as a GitHub Issue in the [specification repository](https://github.com/modelcontextprotocol/modelcontextprotocol). The standard SEP workflow is:
 
-1. You, the SEP author, create a [well-formatted](#sep-format) GitHub Issue with the `SEP` and `proposal` tags. The SEP number is the same as the Github Issue number, the two can be used interchangably.
-2. Core Maintainers and Maintainers will regularly go over the list of open proposals to determine which proposals to sponsor. You can tag relevant maintainers from [the maintainer list](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/main/MAINTAINERS.md) in your proposal.
+1. You, the SEP author, create a [well-formatted](#sep-format) GitHub Issue with the `SEP` and `proposal` tags. The SEP number is the same as the GitHub Issue number, the two can be used interchangably.
+2. Find a Core Maintainer or Maintainer to sponsor your proposal. Core Maintainers and Maintainers will regularly go over the list of open proposals to determine which proposals to sponsor. You can tag relevant maintainers from [the maintainer list](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/main/MAINTAINERS.md) in your proposal.
 3. Once a sponsor is found, the GitHub Issue is assigned to the sponsor. The sponsor will add the `draft` tag, ensure the SEP number is in the title, and assign a milestone.
 4. The sponsor will informally review the proposal and may request changes based on community feedback. When ready for formal review, the sponsor will add the `in-review` tag.
 5. After the `in-review` tag is added, the SEP enters formal review by the Core Maintainers team. The SEP may be accepted, rejected, or returned for revision.