update error message

src/compiler/compile/compiler_errors.ts

@@ -260,7 +260,7 @@ export default {
 	},
 	invalid_const_placement: {
 		code: 'invalid-const-placement',
-		message: '{@const} must be the immediate child of {#if}, {#else}, {#each}, {:then}, {:catch}, <svelte:fragment> or <Component>'
+		message: '{@const} must be the immediate child of {#if}, {:else if}, {:else}, {#each}, {:then}, {:catch}, <svelte:fragment> or <Component>'
 	},
 	invalid_const_declaration: (name: string) => ({
 		code: 'invalid-const-declaration',

test/validator/samples/const-tag-placement-1/errors.json

@@ -1,7 +1,7 @@
 [
 	{
 		"code": "invalid-const-placement",
-		"message": "{@const} must be the immediate child of {#if}, {#else}, {#each}, {:then}, {:catch}, <svelte:fragment> or <Component>",
+		"message": "{@const} must be the immediate child of {#if}, {:else if}, {:else}, {#each}, {:then}, {:catch}, <svelte:fragment> or <Component>",
 		"start": { "line": 5, "column": 0, "character": 36 },
 		"end": { "line": 5, "column": 18, "character": 54 },
 		"pos": 36

test/validator/samples/const-tag-placement-2/errors.json

@@ -1,7 +1,7 @@
 [
 	{
 		"code": "invalid-const-placement",
-		"message": "{@const} must be the immediate child of {#if}, {#else}, {#each}, {:then}, {:catch}, <svelte:fragment> or <Component>",
+		"message": "{@const} must be the immediate child of {#if}, {:else if}, {:else}, {#each}, {:then}, {:catch}, <svelte:fragment> or <Component>",
 		"start": { "line": 7, "column": 4, "character": 63 },
 		"end": { "line": 7, "column": 18, "character": 77 },
 		"pos": 63