[docs] Advise users not to specify the version explicitly

doc/02-libraries.md

@@ -63,6 +63,9 @@ you can just add a `version` field:
         "version": "1.0.0"
     }
 
+> **Note:** You should avoid specifying the version field explicitly, because
+> for tags the value must match the tag name.
+
 ### Tags
 
 For every tag that looks like a version, a package version of that tag will be
@@ -78,8 +81,6 @@ Here are a few examples of valid tag names:
     v2.0.0-alpha
     v2.0.4-p1
 
-> **Note:** If you specify an explicit version in `composer.json`, the tag name must match the specified version.
-
 ### Branches
 
 For every branch, a package development version will be created. If the branch