Backport of mozilla-firefox/firefox commit 9a1535227ce2f95390108747658ad3d0541db259
("Bug 2083543 - Use a non-capturing string token pattern in manifestparser's
expression scanner"), fixed upstream in Firefox 161.

Python 3.15 makes re.Scanner reject patterns with capturing groups
("ValueError: Cannot use capturing groups in re.Scanner"), so every test
manifest condition (skip-if/run-if) failed to parse. The build itself never
evaluates them; src_test (mach cppunittest) does.

diff --git a/testing/mozbase/manifestparser/manifestparser/expression.py b/testing/mozbase/manifestparser/manifestparser/expression.py
index cde2f9ccd697f..e70e9c4f02ad2 100644
--- a/testing/mozbase/manifestparser/manifestparser/expression.py
+++ b/testing/mozbase/manifestparser/manifestparser/expression.py
@@ -190,7 +190,7 @@ def scan(text):
             (r"true|false", bool_token),
             (r"[a-zA-Z_]\w*", ident_token),
             (r"[0-9]+", int_token),
-            (r'("[^"]*")|(\'[^\']*\')', string_token),
+            (r'"[^"]*"|\'[^\']*\'', string_token),
             (r"==", eq_op_token()),
             (r"!=", neq_op_token()),
             (r"<=", le_op_token()),