Remove invalid less selector for less4j
Remove invalid less selector for less4j

time-grid.less has a dangling child selector (`.rbc-row > {`) which is technically illegal less syntax. The normal js-based less compiler everyone uses will ignore the child selector and emit css anyway, but alternative less compilers (like the java-based less4j) have stricter syntax requirements and error-out when they encounter this construct.

Patch removes the dangling child selector.
elationemr/react-big-calendar