starmath: Elements dock: add missing scalable braces

RID_SLRBRACEX was missing in the Elements dock.

Change-Id: Id8b2035b603938dea774ac2cfe1ef5aaff4dae54
starmath: Elements dock: add missing reverse circumflex

Change-Id: I63c7caec6c2c630cf1ce67a4e0f71694475e83bc