fix(@angular/build): coverage reporter option

The coverage reporters option is `reporter`, see https://vitest.dev/config/#coverage-reporter

Author: cexbrayat

packages/angular/build/src/builders/unit-test/builder.ts

@@ -236,7 +236,7 @@ export async function* execute(
             exclude: normalizedOptions.codeCoverage?.exclude ?? [],
             // Special handling for `reporter` due to an undefined value causing upstream failures
             ...(normalizedOptions.codeCoverage?.reporters
-              ? { reporters: normalizedOptions.codeCoverage.reporters }
+              ? { reporter: normalizedOptions.codeCoverage.reporters }
               : {}),
           },
           ...debugOptions,