regex.pcre: fix test, for systems that also have done v install pcre

Author: spytheman

vlib/regex/pcre/regex_test.v

@@ -5,7 +5,7 @@ Copyright (c) 2026 Dario Deledda. All rights reserved.
 Use of this source code is governed by an MIT license
 that can be found in the LICENSE file.
 */
-import pcre
+import regex.pcre
 
 fn main() {
 	println('Running pcre tests...\n')