Attach (recommended) or Link to PDF file here:
https://bitcoin.org/bitcoin.pdf

Configuration:
- Web browser and its version: all
- Operating system and its version: all
- PDF.js version: tested with 2.9.11, but most likely all versions
- Is a browser extension: no

Steps to reproduce the problem:
1. Type "a purely" (single space between "a" and "purely") - doesn't find anything
2. Type "a  purely" (two spaces between "a" and "purely") - finds the phrase

Sometimes even 3 spaces are necessary.

What is the expected behavior? (add screenshot)
![Screenshot from 2021-04-08 13-00-03](https://user-images.githubusercontent.com/6362989/114008903-57639a00-986b-11eb-903a-92bbebbd922b.png)

What went wrong? (add screenshot)
![Screenshot from 2021-04-08 13-01-53](https://user-images.githubusercontent.com/6362989/114008810-44e96080-986b-11eb-8232-f58a62ed7899.png)

This affects many PDFs because justify alignment is common enough.
buildGetDocumentParams(basicApiFileName, { pdfBug: true })
      );
      const pdfDoc = await loadingTask.promise;
      const pdfPage = await pdfDoc.getPage(1);
      const viewport = pdfPage.getViewport({ scale: 1 });
      const canvasAndCtx = CanvasFactory.create(
        viewport.width,
        viewport.height
      );
      const renderTask = pdfPage.render({
        canvasContext: canvasAndCtx.context,
        canvasFactory: CanvasFactory,
        viewport,
      });
      expect(renderTask instanceof RenderTask).toEqual(true);
      await renderTask.promise;
      const stats = pdfPage.stats;
      expect(stats instanceof StatTimer).toEqual(true);
      expect(stats.times.length).toEqual(3);
      const [statEntryOne, statEntryTwo, statEntryThree] = stats.times;
      expect(statEntryOne.name).toEqual("Page Request");
      expect(statEntryOne.end - statEntryOne.start).toBeGreaterThanOrEqual(0);
      expect(statEntryTwo.name).toEqual("Rendering");
      expect(statEntryTwo.end - statEntryTwo.start).toBeGreaterThan(0);
      expect(statEntryThree.name).toEqual("Overall");
      expect(statEntryThree.end - statEntryThree.start).toBeGreaterThan(0);
      CanvasFactory.destroy(canvasAndCtx);
      await loadingTask.destroy();
    });
    it("cancels rendering of page", async function () {