Add `/framework-*/build` to .gitignore

Due to the introduction of the `framework-api` project in the main branch,
we now have 3 `framework-*` projects that should be ignored. I have
therefore removed `/framework-bom/build` and `/framework-docs/build` and
added `/framework-*/build` to ignore all 3 framework projects.

See gh-31049

.gitignore

@@ -21,8 +21,7 @@ derby.log
 /build
 buildSrc/build
 /spring-*/build
-/framework-bom/build
-/framework-docs/build
+/framework-*/build
 /integration-tests/build
 /src/asciidoc/build
 spring-test/test-output/