String literal mutator should not mutate DeclareModule node types

[nicojs]

Originally from @brodybits 🤟 in #2340

When I tried mutate on packages/react-devtools-extensions:

  mutate: [
    'packages/react-devtools-extensions/**/*.js',
    '!packages/react-devtools-extensions/node_modules/**/*.js',
    '!packages/react-devtools-extensions/__tests__/**/*.js',
  ],

it gave me this error:

21:01:38 (45459) ERROR Stryker an error occurred Error: Error while placing mutants of type(s) "StringLiteral" on 52:15 with conditionalExpressionMutantPlacer. TypeError: Property id of DeclareModule expected node to be of a type ["Identifier","StringLiteral"] but instead got "SequenceExpression"
    at Object.validate (/home/brodybits/react/node_modules/@stryker-mutator/instrumenter/node_modules/@babel/types/lib/definitions/utils.js:132:11)
    at validateField (/home/brodybits/react/node_modules/@stryker-mutator/instrumenter/node_modules/@babel/types/lib/validators/validate.js:24:9)
    at Object.validate (/home/brodybits/react/node_modules/@stryker-mutator/instrumenter/node_modules/@babel/types/lib/validators/validate.js:17:3)
    at NodePath._replaceWith (/home/brodybits/react/node_modules/@stryker-mutator/instrumenter/node_modules/@babel/traverse/lib/path/replacement.js:172:7)
    at NodePath.replaceWith (/home/brodybits/react/node_modules/@stryker-mutator/instrumenter/node_modules/@babel/traverse/lib/path/replacement.js:156:8)
    at conditionalExpressionMutantPlacer (/home/brodybits/react/node_modules/@stryker-mutator/instrumenter/dist/src/mutant-placers/conditional-expression-mutant-placer.js:17:14)
    at Object.placeMutant (/home/brodybits/react/node_modules/@stryker-mutator/instrumenter/dist/src/mutant-placers/index.js:20:21)
    at exit (/home/brodybits/react/node_modules/@stryker-mutator/instrumenter/dist/src/transformers/babel-transformer.js:28:34)
    at NodePath._call (/home/brodybits/react/node_modules/@stryker-mutator/instrumenter/node_modules/@babel/traverse/lib/path/context.js:55:20)
    at NodePath.call (/home/brodybits/react/node_modules/@stryker-mutator/instrumenter/node_modules/@babel/traverse/lib/path/context.js:38:14)
    at Object.placeMutant (/home/brodybits/react/node_modules/@stryker-mutator/instrumenter/dist/src/mutant-placers/index.js:25:23)
    at exit (/home/brodybits/react/node_modules/@stryker-mutator/instrumenter/dist/src/transformers/babel-transformer.js:28:34)
    at NodePath._call (/home/brodybits/react/node_modules/@stryker-mutator/instrumenter/node_modules/@babel/traverse/lib/path/context.js:55:20)
    at NodePath.call (/home/brodybits/react/node_modules/@stryker-mutator/instrumenter/node_modules/@babel/traverse/lib/path/context.js:38:14)
    at NodePath.visit (/home/brodybits/react/node_modules/@stryker-mutator/instrumenter/node_modules/@babel/traverse/lib/path/context.js:101:8)
    at TraversalContext.visitQueue (/home/brodybits/react/node_modules/@stryker-mutator/instrumenter/node_modules/@babel/traverse/lib/context.js:112:16)
    at TraversalContext.visitSingle (/home/brodybits/react/node_modules/@stryker-mutator/instrumenter/node_modules/@babel/traverse/lib/context.js:84:19)
    at TraversalContext.visit (/home/brodybits/react/node_modules/@stryker-mutator/instrumenter/node_modules/@babel/traverse/lib/context.js:140:19)
    at Function.traverse.node (/home/brodybits/react/node_modules/@stryker-mutator/instrumenter/node_modules/@babel/traverse/lib/index.js:82:17)
    at NodePath.visit (/home/brodybits/react/node_modules/@stryker-mutator/instrumenter/node_modules/@babel/traverse/lib/path/context.js:99:18)