renamed lemma filter_image_mset to filter_mset_image_mset

--- a/NEWS	Tue Mar 04 13:10:47 2025 +0100
+++ b/NEWS	Tue Mar 04 15:19:08 2025 +0100
@@ -15,6 +15,8 @@
       monotone_on_sup_fun
 
 * Theory "HOL-Library.Multiset":
+  - Renamed lemmas. Minor INCOMPATIBILITY.
+      filter_image_mset ~> filter_mset_image_mset
   - Added lemmas.
       filter_mset_mono_strong
       filter_mset_sum_list

--- a/src/HOL/Library/Multiset.thy	Tue Mar 04 13:10:47 2025 +0100
+++ b/src/HOL/Library/Multiset.thy	Tue Mar 04 15:19:08 2025 +0100
@@ -1745,7 +1745,7 @@
      image_mset f (filter_mset P A) + image_mset g (filter_mset (\<lambda>x. \<not>P x) A)"
   by (induction A) auto
 
-lemma filter_image_mset:
+lemma filter_mset_image_mset:
   "filter_mset P (image_mset f A) = image_mset f (filter_mset (\<lambda>x. P (f x)) A)"
   by (induction A) auto