Fix for feature/multi qr code reader

[shahrin014]

Fixed the following to allow tests to run

• Removed duplicate import (and shifted it's position to prevent merge conflict with master later)
• Explicitly specify assert function return value, to prevent typescript errors:

src/test/core/pdf417/decoder/PDF417Decoder.spec.ts:131:5 - error TS2775: Assertions require every name in the call target to be declared with an explicit type annotation.

131     assertEquals(260013, resultMetadata.getChecksum());
        ~~~~~~~~~~~~

  src/test/core/util/AssertUtils.ts:23:14
    23 export const assertEquals = assert.strictEqual;
                    ~~~~~~~~~~~~
    'assertEquals' needs an explicit type annotation.