label desktop-helper as fx-compatible and set recommended maxVersion; r=vingtetun, a=NPOTB

(cherry picked from commit 7315f49c817f56b57ab453bf184f0587cdd1795e)
Merge pull request #11190 from mykmelez/v1-train-fx-version

bug 898130 - label desktop-helper as fx-compatible and set recommended maxVersion; r=vingtetun, a=NPOTB