Update Atmosphere to resolve problems in servlets with multiple mappings

[Artur-]

Fixes #8734

---

This change is 

[hesara]

Reviewed 2 of 2 files at r1.
Review status: all files reviewed at latest revision, 1 unresolved discussion, some commit checks failed.

---

pom.xml, line 37 at r1 (raw file):

        <vaadin.sass.version>0.9.13</vaadin.sass.version>
        <!-- Note that this should be kept in sync with the class Constants -->
        <atmosphere.runtime.version>2.4.5.vaadin2</atmosphere.runtime.version>

version not in Maven Central, and I didn't see any recent builds for it on r2d2 either - ok to submit this change once the version is available

---

Comments from Reviewable

[Artur-]

Review status: all files reviewed at latest revision, 1 unresolved discussion, some commit checks failed.

---

pom.xml, line 37 at r1 (raw file):

Previously, hesara (Henri Sara) wrote…

version not in Maven Central, and I didn't see any recent builds for it on r2d2 either - ok to submit this change once the version is available

vaadin/atmosphere#1

---

Comments from Reviewable