Wizard: Update search input placeholders

The placeholders we tend to use are usually quite specific. "Type to search" felt quite vague for some reason. Also repositories had no placeholder, I believe "filter" is clearer than "search" here as we're not fetching any results, just filtering through the already existing list of repositories.

src/Components/CreateImageWizard/steps/Packages/Packages.tsx

@@ -1243,7 +1243,7 @@ const Packages = () => {
             <ToolbarItem variant="search-filter">
               <SearchInput
                 type="text"
-                placeholder="Type to search"
+                placeholder="Search packages"
                 aria-label="Search packages"
                 data-testid="packages-search-input"
                 value={searchTerm}

src/Components/CreateImageWizard/steps/Repositories/Repositories.tsx

@@ -524,7 +524,8 @@ const Repositories = () => {
             </ToolbarItem>
             <ToolbarItem variant="search-filter">
               <SearchInput
-                aria-label="Search repositories"
+                placeholder="Filter repositories"
+                aria-label="Filter repositories"
                 onChange={handleFilterRepositories}
                 value={filterValue}
                 onClear={() => setFilterValue('')}