build.yml: Change python-versions to leave off patch version.

This makes sure that the build uses the latest patch version for each
python major.minor. Keep the pre-release for 3.13 explicit as I don't
know how that will work before the first 3.13 release is out.

Also make each version number be on a separate line so that adding and
removing python versions is easier to see in diffs, e.g., like this:

https://github.com/google/earthengine-api/blob/e44bb391af90c9b7dfde79d95b55116e79d0d6bf/.github/workflows/ci-tests.yml#L17

Author: schwehr

.github/workflows/build.yml

@@ -15,7 +15,18 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["2.7.18", "3.5.10", "3.6.15", "3.7.17", "3.8.18", "3.9.18",  "3.10.13", "3.11.7", "3.12.1", "3.13.0a2"]
+        python-version: [
+            "2.7",
+            "3.5",
+            "3.6",
+            "3.7",
+            "3.8",
+            "3.9",
+            "3.10",
+            "3.11",
+            "3.12",
+            "3.13.0a2",
+        ]
 
     runs-on: ubuntu-latest
     container: