chore(deps): update readthedocs/ubuntu docker tag to v26 (#5771)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>
Co-authored-by: Dave Lane <42013603+ReenigneArcher@users.noreply.github.com>

.readthedocs.yaml

@@ -6,10 +6,10 @@
 version: 2
 
 build:
-  os: ubuntu-24.04
+  os: ubuntu-26.04
   tools:
     nodejs: "24"
-    python: "miniconda-latest"
+    python: "miniforge3-26.3"
   jobs:
     build:
       html:

gh-pages-template/.readthedocs.yaml

@@ -5,7 +5,7 @@
 version: 2
 
 build:
-  os: ubuntu-24.04
+  os: ubuntu-26.04
   tools:
     ruby: "3.3"
   apt_packages: