HDFS-17152. Fix the documentation of count command in FileSystemShell.md.

[hfutatzhanghb]

Description of PR

Please see HDFS-17152.

[hadoop-yetus]

💔 -1 overall

Vote	Subsystem	Runtime	Logfile	Comment
+0 🆗	reexec	0m 54s		Docker mode activated.
			_ Prechecks _
+1 💚	dupname	0m 0s		No case conflicting files found.
+0 🆗	codespell	0m 0s		codespell was not available.
+0 🆗	detsecrets	0m 0s		detect-secrets was not available.
+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	44m 28s	/branch-mvninstall-root.txt	root in trunk failed.
+1 💚	mvnsite	1m 33s		trunk passed
+1 💚	shadedclient	84m 55s		branch has no errors when building and testing our client artifacts.
			_ Patch Compile Tests _
+1 💚	mvninstall	0m 57s		the patch passed
+1 💚	blanks	0m 0s		The patch has no blanks issues.
+1 💚	mvnsite	1m 19s		the patch passed
+1 💚	shadedclient	39m 15s		patch has no errors when building and testing our client artifacts.
			_ Other Tests _
+1 💚	asflicense	0m 35s		The patch does not generate ASF License warnings.
		130m 41s

Subsystem	Report/Notes
Docker	ClientAPI=1.43 ServerAPI=1.43 base: https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-5939/1/artifact/out/Dockerfile
GITHUB PR	#5939
Optional Tests	dupname asflicense mvnsite codespell detsecrets markdownlint
uname	Linux 94c4904c66c7 4.15.0-212-generic #223-Ubuntu SMP Tue May 23 13:09:22 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/bin/hadoop.sh
git revision	trunk / 04b9774
Max. process+thread count	586 (vs. ulimit of 5500)
modules	C: hadoop-common-project/hadoop-common U: hadoop-common-project/hadoop-common
Console output	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-5939/1/console
versions	git=2.25.1 maven=3.6.3
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[hadoop-yetus]

🎊 +1 overall

Vote	Subsystem	Runtime	Logfile	Comment
+0 🆗	reexec	0m 55s		Docker mode activated.
			_ Prechecks _
+1 💚	dupname	0m 0s		No case conflicting files found.
+0 🆗	codespell	0m 0s		codespell was not available.
+0 🆗	detsecrets	0m 0s		detect-secrets was not available.
+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	47m 54s		trunk passed
+1 💚	mvnsite	1m 30s		trunk passed
+1 💚	shadedclient	87m 10s		branch has no errors when building and testing our client artifacts.
			_ Patch Compile Tests _
+1 💚	mvninstall	0m 56s		the patch passed
+1 💚	blanks	0m 0s		The patch has no blanks issues.
+1 💚	mvnsite	1m 18s		the patch passed
+1 💚	shadedclient	38m 41s		patch has no errors when building and testing our client artifacts.
			_ Other Tests _
+1 💚	asflicense	0m 36s		The patch does not generate ASF License warnings.
		132m 37s

Subsystem	Report/Notes
Docker	ClientAPI=1.43 ServerAPI=1.43 base: https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-5939/2/artifact/out/Dockerfile
GITHUB PR	#5939
Optional Tests	dupname asflicense mvnsite codespell detsecrets markdownlint
uname	Linux db137d81e4ef 4.15.0-212-generic #223-Ubuntu SMP Tue May 23 13:09:22 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/bin/hadoop.sh
git revision	trunk / 18922ee
Max. process+thread count	533 (vs. ulimit of 5500)
modules	C: hadoop-common-project/hadoop-common U: hadoop-common-project/hadoop-common
Console output	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-5939/2/console
versions	git=2.25.1 maven=3.6.3
Powered by	Apache Yetus 0.14.0 https://yetus.apache.org

This message was automatically generated.

[slfan1989]

LGTM.

[hfutatzhanghb]

@slfan1989 Hi, sir. Could we push this simple modification forward when you have free time? Thanks a lot~