Revert "[sonic-slave]: Fix redis version during pip3 install (#9317)"

This reverts commit da1503d.

Author: qiluo-msft

sonic-slave-bullseye/Dockerfile.j2

@@ -447,7 +447,7 @@ RUN pip3 install "PyYAML==5.4.1"
 RUN pip3 install "lxml==4.6.2"
 
 # For sonic-platform-common testing
-RUN pip3 install redis==3.5.3
+RUN pip3 install redis
 
 # For vs image build
 RUN pip3 install pexpect==4.8.0

sonic-slave-buster/Dockerfile.j2

@@ -466,7 +466,7 @@ RUN pip2 install "lxml==4.6.5"
 RUN pip3 install "lxml==4.6.5"
 
 # For sonic-platform-common testing
-RUN pip3 install redis==3.5.3
+RUN pip3 install redis
 
 # For vs image build
 RUN pip2 install pexpect==4.6.0

sonic-slave-stretch/Dockerfile.j2

@@ -371,7 +371,7 @@ RUN pip3 install "lxml==4.6.5"
 
 
 # For sonic-platform-common testing
-RUN pip3 install redis==3.5.3
+RUN pip3 install redis
 
 # For vs image build
 RUN pip2 install pexpect==4.6.0