Update releases table and base branches

Signed-off-by: Hasan Turken <[email protected]>

Author: turkenh

.github/renovate.json5

@@ -14,7 +14,6 @@
   // PLEASE UPDATE THIS WHEN RELEASING.
   "baseBranches": [
     "main",
-    "release-1.15",
     "release-1.16",
     "release-1.17",
     "release-1.18"

README.md

@@ -24,12 +24,12 @@ documentation].
 
 | Release | Release Date  |   EOL    |
 |:-------:|:-------------:|:--------:|
-|  v1.15  | Feb 15, 2024  | Nov 2024 |
 |  v1.16  | May 15, 2024  | Feb 2025 |
 |  v1.17  | Aug 29, 2024  | May 2025 |
 |  v1.18  | Early Nov '24 | Aug 2025 |
 |  v1.19  | Early Feb '25 | Nov 2025 |
 |  v1.20  | Early May '25 | Feb 2026 |
+|  v1.21  | Early Aug '25 | May 2026 |
 
 You can subscribe to the [community calendar] to track all release dates, and
 find the most recent releases on the [releases] page.