Replace ZoL with OpenZFS where applicable

Afterward, git grep ZoL matches:
  * README.md:  * [ZoL Site](https://zfsonlinux.org)
  - Correct
  * etc/default/zfs.in:# ZoL userland configuration.
  - Changing this would induce a needless upgrade-check,
    if the user has modified the configuration;
    this can be updated the next time the defaults change
  * module/zfs/dmu_send.c:   * ZoL < 0.7 does not handle [...]
  - Before 0.7 is ZoL, so fair enough

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Issue #11956

scripts/zimport.sh

@@ -1,10 +1,10 @@
 #!/usr/bin/env bash
 #
 # Verify that an assortment of known good reference pools can be imported
-# using different versions of the ZoL code.
+# using different versions of OpenZFS code.
 #
 # By default references pools for the major ZFS implementation will be
-# checked against the most recent ZoL tags and the master development branch.
+# checked against the most recent OpenZFS tags and the master development branch.
 # Alternate tags or branches may be verified with the '-s <src-tag> option.
 # Passing the keyword "installed" will instruct the script to test whatever
 # version is installed.
@@ -98,7 +98,7 @@ OPTIONS:
 	-c                No color
 	-k                Keep temporary directory
 	-r <repo>         Source repository ($REPO)
-	-s <src-tag>...   Verify ZoL versions with the listed tags
+	-s <src-tag>...   Verify OpenZFS versions with the listed tags
 	-i <pool-dir>     Pool image directory
 	-p <pool-tag>...  Verify pools created with the listed tags
 	-f <path>         Temporary directory to use