[Infra] Ignore release_report.md from formatter (#7427)

The file is auto generated and not intended to be consumed directly,
thus formatting isn't a priority. Also, since it's generated during the
release process, the only way of running the formatter would be checking
out the branch, which is not necessary for any other step of the
process.

Author: rlazo

build.gradle.kts

@@ -62,7 +62,7 @@ fun Project.applySpotless() {
     }
     format("styling") {
       target("src/**/*.md", "*.md", "docs/**/*.md")
-      targetExclude("**/third_party/**", "src/test/resources/**")
+      targetExclude("**/third_party/**", "src/test/resources/**", "release_report.md")
       prettier().config(mapOf("printWidth" to 100, "proseWrap" to "always"))
     }
   }