Fix grammar in README events calendar description #3542

Job	Run time
check-skip	3s
Build Apache Cloudberry RPM	14m 27s
prepare-test-matrix	4s
RPM Install Test Apache Cloudberry	2m 58s
pax-ic-good-opt-on	27m 0s
ic-good-opt-off	25m 18s
ic-isolation2-crash	4m 47s
ic-cbdb-parallel	28m 56s
pax-ic-isolation2-opt-off	23m 1s
ic-fixme	3m 31s
ic-contrib	4m 14s
ic-good-opt-on	30m 20s
ic-isolation2	36m 43s
ic-diskquota	10m 57s
pax-ic-good-opt-off	20m 12s
ic-isolation2-hot-standby	4m 48s
ic-expandshrink	4m 45s
pax-ic-isolation2-opt-on	23m 35s
ic-gpcontrib	4m 20s
ic-singlenode	8m 7s
ic-resgroup-v2	20m 18s
ic-parallel-retrieve-cursor	4m 53s
Generate Apache Cloudberry Build Report	2s
	5h 3m 19s

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