Fix #527: Update team names from LaCE and CD to LEAP and CORE

[poorvith-mp]

Overview

Fixes #527.

Updates references to outdated team names across the documentation:

• \LaCE Team\ / \LaCE\ -> \LEAP Team\ / \LEAP\
• \CD Team\ / \CD\ -> \CORE Team\ / \CORE\
• \Learner and Creator Experience\ -> \LEAP Team (Learners, Educators, Allies, and Parents)\
• \Contributor Dashboard\ team references -> \CORE Team (Creators, Operations, Reviewers and Editors)\

What changed

• _Sidebar.md: Updated quick link heading from LaCE/CD to LEAP/CORE.
• \Contributing-code-to-Oppia.md: Updated team project board links and onboarding guide references.
• \Triaging-process.md: Updated team triage labels and contacts to LEAP Quality and CORE Team.
• \Google-Summer-of-Code-2026.md: Updated team meeting list and clarified dashboard references.
• \Google-Summer-of-Code-2020.md\ through \Google-Summer-of-Code-2025.md: Updated team names in historical project ideas and mentor listings while preserving all context and URLs.

Verification

• Ran \python scripts/linter.py\ — passed with 0 errors.
• Verified across the docs that no outdated team references remain.