Standardise comment explaining why extensible predicates must be defined

csharp/ql/lib/ext/empty.model.yml

@@ -1,4 +1,6 @@
 extensions:
+  # Make sure that the extensible model predicates have at least one definition
+  # to avoid errors about an undefined extensionals.
   - addsTo:
       pack: codeql/csharp-all
       extensible: sourceModel

go/ql/lib/ext/empty.model.yml

@@ -1,5 +1,6 @@
 extensions:
-  # Make sure that the extensible model predicates are at least defined as empty.
+  # Make sure that the extensible model predicates have at least one definition
+  # to avoid errors about an undefined extensionals.
   - addsTo:
       pack: codeql/go-all
       extensible: sourceModel

java/ql/lib/ext/empty.model.yml

@@ -1,5 +1,6 @@
 extensions:
-  # Make sure that the extensible model predicates are at least defined as empty.
+  # Make sure that the extensible model predicates have at least one definition
+  # to avoid errors about an undefined extensionals.
   - addsTo:
       pack: codeql/java-all
       extensible: sourceModel

java/ql/lib/ext/experimental/empty.model.yml

@@ -1,6 +1,6 @@
-# Define the extensible prediactes related to experimental queries
-# to at least be empty.
 extensions:
+  # Make sure that the extensible model predicates have at least one definition
+  # to avoid errors about an undefined extensionals.
   - addsTo:
       pack: codeql/java-all
       extensible: experimentalSourceModel

javascript/ql/lib/semmle/javascript/frameworks/data/internal/empty.model.yml

@@ -1,5 +1,6 @@
 extensions:
-  # Contribute empty data sets to avoid errors about an undefined extensionals
+  # Make sure that the extensible model predicates have at least one definition
+  # to avoid errors about an undefined extensionals.
   - addsTo:
       pack: codeql/javascript-all
       extensible: sourceModel

python/ql/lib/semmle/python/frameworks/data/internal/empty.model.yml

@@ -1,5 +1,6 @@
 extensions:
-  # Contribute empty data sets to avoid errors about an undefined extensionals
+  # Make sure that the extensible model predicates have at least one definition
+  # to avoid errors about an undefined extensionals.
   - addsTo:
       pack: codeql/python-all
       extensible: sourceModel

ruby/ql/lib/codeql/ruby/frameworks/data/internal/empty.model.yml

@@ -1,5 +1,6 @@
 extensions:
-  # Contribute empty data sets to avoid errors about an undefined extensionals
+  # Make sure that the extensible model predicates have at least one definition
+  # to avoid errors about an undefined extensionals.
   - addsTo:
       pack: codeql/ruby-all
       extensible: sourceModel