HBASE-24763 Remove 2.1 Documentation direct link from website

[petersomogyi]

2.1 is EOM so the 2.1 Documentation link can be removed.
The content is still available under https://hbase.apache.org/2.1

[Apache-HBase]

🎊 +1 overall

Vote	Subsystem	Runtime	Comment
+0 🆗	reexec	0m 38s	Docker mode activated.
-0 ⚠️	yetus	0m 3s	Unprocessed flag(s): --brief-report-file --spotbugs-strict-precheck --whitespace-eol-ignore-list --whitespace-tabs-ignore-list --quick-hadoopcheck
		_ Prechecks _
		_ master Compile Tests _
		_ Patch Compile Tests _
		_ Other Tests _
		1m 58s

Subsystem	Report/Notes
Docker	Client=19.03.12 Server=19.03.12 base: https://builds.apache.org/job/HBase-PreCommit-GitHub-PR/job/PR-2129/1/artifact/yetus-jdk11-hadoop3-check/output/Dockerfile
GITHUB PR	#2129
Optional Tests
uname	Linux 296c30331b2f 4.15.0-58-generic #64-Ubuntu SMP Tue Aug 6 11:12:41 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/hbase-personality.sh
git revision	master / 8191fbd
Max. process+thread count	51 (vs. ulimit of 12500)
modules	C: . U: .
Console output	https://builds.apache.org/job/HBase-PreCommit-GitHub-PR/job/PR-2129/1/console
versions	git=2.17.1 maven=(cecedd343002696d0abb50b32b541b8a6ba2883f)
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[Apache-HBase]

🎊 +1 overall

Vote	Subsystem	Runtime	Comment
+0 🆗	reexec	2m 22s	Docker mode activated.
-0 ⚠️	yetus	0m 3s	Unprocessed flag(s): --brief-report-file --spotbugs-strict-precheck --whitespace-eol-ignore-list --whitespace-tabs-ignore-list --quick-hadoopcheck
		_ Prechecks _
		_ master Compile Tests _
		_ Patch Compile Tests _
		_ Other Tests _
		3m 39s

Subsystem	Report/Notes
Docker	Client=19.03.12 Server=19.03.12 base: https://builds.apache.org/job/HBase-PreCommit-GitHub-PR/job/PR-2129/1/artifact/yetus-jdk8-hadoop3-check/output/Dockerfile
GITHUB PR	#2129
Optional Tests
uname	Linux cdafc5166243 4.15.0-101-generic #102-Ubuntu SMP Mon May 11 10:07:26 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/hbase-personality.sh
git revision	master / 8191fbd
Max. process+thread count	42 (vs. ulimit of 12500)
modules	C: . U: .
Console output	https://builds.apache.org/job/HBase-PreCommit-GitHub-PR/job/PR-2129/1/console
versions	git=2.17.1 maven=(cecedd343002696d0abb50b32b541b8a6ba2883f)
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[Apache-HBase]

🎊 +1 overall

Vote	Subsystem	Runtime	Comment
+0 🆗	reexec	0m 30s	Docker mode activated.
		_ Prechecks _
+1 💚	dupname	0m 0s	No case conflicting files found.
+1 💚	@author	0m 0s	The patch does not contain any @author tags.
		_ master Compile Tests _
+1 💚	mvninstall	3m 45s	master passed
+1 💚	mvnsite	10m 11s	master passed
		_ Patch Compile Tests _
+1 💚	mvninstall	3m 28s	the patch passed
+1 💚	mvnsite	10m 7s	the patch passed
+1 💚	whitespace	0m 1s	The patch has no whitespace issues.
+1 💚	xml	0m 2s	The patch has no ill-formed XML file.
		_ Other Tests _
+1 💚	asflicense	0m 21s	The patch does not generate ASF License warnings.
		30m 4s

Subsystem	Report/Notes
Docker	Client=19.03.12 Server=19.03.12 base: https://builds.apache.org/job/HBase-PreCommit-GitHub-PR/job/PR-2129/1/artifact/yetus-general-check/output/Dockerfile
GITHUB PR	#2129
Optional Tests	dupname asflicense mvnsite xml
uname	Linux 8f9e81af8b7a 4.15.0-58-generic #64-Ubuntu SMP Tue Aug 6 11:12:41 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/hbase-personality.sh
git revision	master / 8191fbd
Max. process+thread count	89 (vs. ulimit of 12500)
modules	C: . U: .
Console output	https://builds.apache.org/job/HBase-PreCommit-GitHub-PR/job/PR-2129/1/console
versions	git=2.17.1 maven=(cecedd343002696d0abb50b32b541b8a6ba2883f)
Powered by	Apache Yetus 0.11.1 https://yetus.apache.org

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