runtime(java): Highlight javaConceptKind modifiers with StorageClass

Stop assigning by default the NonText highlighting group for
javaConceptKind modifiers since its colour is hardly
distinguishable from a background colour for a range of
colour schemes.

fixes #15237
related #15238
closes: #15664

Co-authored-by: Dexter Gaon-Shatford <dexter@gaonshatford.ca>
Signed-off-by: Aliaksei Budavei <0x000c70@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/syntax/java.vim b/runtime/syntax/java.vim
index 293d63c..d3b59c1 100644
--- a/runtime/syntax/java.vim
+++ b/runtime/syntax/java.vim
@@ -3,7 +3,7 @@
 " Maintainer:		Aliaksei Budavei <0x000c70 AT gmail DOT com>
 " Former Maintainer:	Claudio Fleiner <claudio@fleiner.com>
 " Repository:		https://github.com/zzzyxwvut/java-vim.git
-" Last Change:		2024 Sep 10
+" Last Change:		2024 Sep 11
 
 " Please check :help java.vim for comments on some of the options available.
 
@@ -663,7 +663,7 @@
 hi def link javaMethodDecl		javaStorageClass
 hi def link javaClassDecl		javaStorageClass
 hi def link javaScopeDecl		javaStorageClass
-hi def link javaConceptKind		NonText
+hi def link javaConceptKind		javaStorageClass
 
 hi def link javaBoolean			Boolean
 hi def link javaSpecial			Special