Update docs to point to 2.6 release notes

Signed-off-by: Remington Steed <rjs7@calvin.edu>
Fix 2.6 Release Notes typos and formatting

This commit fixes an AsciiDoc URL processing bug by marking two fake URLs
as lines of code. It also fixes a few small typos and misspellings.

Signed-off-by: Remington Steed <rjs7@calvin.edu>