images: Disable google-nyan-big & google-nyan-blaze on master

The images have been failing for quite a while and nobody seems to bother to fix them, so disable building the images.

Draft: actually not sure if they even build on v24.06, currently nothing builds on stable.

bpo/config/const/images.py

@@ -266,7 +266,8 @@ images = {
     },
     "google-nyan-big": {
         "branches": [
-            "master",
+            # Disabled on master:
+            # https://gitlab.postmarketos.org/postmarketOS/pmaports/-/issues/3186
             "v24.06",
         ],
         "branch_configs": {
@@ -281,7 +282,8 @@ images = {
     },
     "google-nyan-blaze": {
         "branches": [
-            "master",
+            # Disabled on master:
+            # https://gitlab.postmarketos.org/postmarketOS/pmaports/-/issues/3186
             "v24.06",
         ],
         "branch_configs": {