YARN-10498. Fix Yarn CapacityScheduler Markdown document

[kevinzhao1661]

I have found CapacityScheduler.md has spelling mistake,so I fix it.

JIRA: https://issues.apache.org/jira/browse/YARN-10498

[hadoop-yetus]

🎊 +1 overall

Vote	Subsystem	Runtime	Logfile	Comment
+0 🆗	reexec	0m 32s		Docker mode activated.
			_ Prechecks _
+1 💚	dupname	0m 0s		No case conflicting files found.
+0 🆗	markdownlint	0m 0s		markdownlint was not available.
+1 💚	@author	0m 0s		The patch does not contain any @author tags.
			_ trunk Compile Tests _
+1 💚	mvninstall	34m 13s		trunk passed
+1 💚	mvnsite	0m 29s		trunk passed
+1 💚	shadedclient	50m 1s		branch has no errors when building and testing our client artifacts.
			_ Patch Compile Tests _
+1 💚	mvninstall	0m 15s		the patch passed
+1 💚	mvnsite	0m 18s		the patch passed
+1 💚	whitespace	0m 0s		The patch has no whitespace issues.
+1 💚	shadedclient	14m 56s		patch has no errors when building and testing our client artifacts.
			_ Other Tests _
+1 💚	asflicense	0m 34s		The patch does not generate ASF License warnings.
		68m 26s

Subsystem	Report/Notes
Docker	ClientAPI=1.40 ServerAPI=1.40 base: https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-2484/1/artifact/out/Dockerfile
GITHUB PR	#2484
Optional Tests	dupname asflicense mvnsite markdownlint
uname	Linux 7eb2e3cdd6fc 4.15.0-60-generic #67-Ubuntu SMP Thu Aug 22 16:55:30 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/bin/hadoop.sh
git revision	trunk / d730294
Max. process+thread count	543 (vs. ulimit of 5500)
modules	C: hadoop-yarn-project/hadoop-yarn/hadoop-yarn-site U: hadoop-yarn-project/hadoop-yarn/hadoop-yarn-site
Console output	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-2484/1/console
versions	git=2.17.1 maven=3.6.0
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[aajisaka]

Merged. Thank you @kevinzhao1661 for your contribution.