Disable 3.15 builds for now

Don't know why ci-scripts isn't building the two dependent
PVA modules PVDATA and PVACCESS in the base-3.15 build. My
.ci-local/default.set was copied from pva2pva; I can't see
anything likely in the .github/workflows/ci-scripts-build.yml
file which was copied from pvAccess.

Author: anjohnson

.github/workflows/ci-scripts-build.yml

@@ -43,12 +43,12 @@ jobs:
       matrix:
         # Job names also name artifacts, character limitations apply
         include:
-          - os: ubuntu-20.04
-            cmp: gcc
-            configuration: default
-            base: "3.15"
-            wine: "64"
-            name: "3.15 Ub-20 gcc-9 + MinGW"
+          #- os: ubuntu-20.04
+          #  cmp: gcc
+          #  configuration: default
+          #  base: "3.15"
+          #  wine: "64"
+          #  name: "3.15 Ub-20 gcc-9 + MinGW"
 
           - os: ubuntu-20.04
             cmp: gcc