Explain patchN syntax situation in a comment

- Related: RHEL-30941

java-17-openjdk.spec

@@ -1843,9 +1843,20 @@ sh %{SOURCE12} %{top_level_dir_name}
 %endif
 
 # Patch the JDK
-# -P N: apply patch number N, same as passing N as a positional argument on rpm >= 4.18
-# -p N: strip N leading slashes from paths
 pushd %{top_level_dir_name}
+# This syntax is deprecated:
+#    %patchN [...]
+# and should be replaced with:
+#    %patch -PN [...]
+# For example:
+#    %patch1001 -p1
+# becomes:
+#    %patch -P1001 -p1
+# The replacement format suggested by recent (circa Fedora 38) RPM
+# deprecation messages:
+#    %patch N [...]
+# is not backward-compatible with prior (circa RHEL-8) versions of
+# rpmbuild.
 %patch -P1 -p1
 %patch -P3 -p1
 %patch -P6 -p1
@@ -2478,6 +2489,7 @@ cjc.mainProgram(args)
 - Update to jdk-17.0.11+7 (EA)
 - Update buildjdkver to match the featurever
 - Use featurever macro to specify fips patch
+- Explain patchN syntax situation in a comment
 - Related: RHEL-30941
 
 * Thu Jan 11 2024 Andrew Hughes <gnu.andrew@redhat.com> - 1:17.0.10.0.7-1