DOCSP-38793 updating minimum ubuntu and RHEL version (#627)

* DOCSP-38793 updating minimum ubuntu version

* DOCSP-38793 removing RHEL7 support

* DOCSP-38793 changing minimum RHEL to 8

Author: ltran-mdb2

source/install.txt

@@ -94,7 +94,7 @@ To download and install |compass|, select your operating system:
 
                |compass-short| requires:
 
-               - 64-bit version of Ubuntu 14.04 or later.
+               - 64-bit version of Ubuntu 16.04 or later.
                - MongoDB 4.2 or later.
 
             .. tab:: .rpm
@@ -105,7 +105,7 @@ To download and install |compass|, select your operating system:
 
                |compass-short| requires:
 
-               - 64-bit version of RHEL 7+ or later.
+               - 64-bit version of RHEL 8+ or later.
                - MongoDB 4.2 or later.
 
 .. tabs-platforms::
@@ -267,4 +267,4 @@ To download and install |compass|, select your operating system:
    :titlesonly:
 
    /upgrade
-   /editions
+   /editions