Update DEPS to latest linter (0.1.26).

* Updated tests to use package `test` (#302).
* Fixed false positive on `[]=` in `always_declare_return_types` (#300).
* New `invariant_booleans` lint.
* New `literal_only_boolean_expressions` lint.
* Fixed `camel_case_types` to allow `$` in identifiers (#290).

BUG=
R=brianwilkerson@google.com

Review URL: https://codereview.chromium.org/2309333002 .

DEPS

@@ -71,7 +71,7 @@ vars = {
   "jinja2_rev": "@2222b31554f03e62600cd7e383376a7c187967a1",
   "json_rpc_2_tag": "@2.0.2",
   "kernel_rev": "@9509d282a62fe025f8d6242bb233b02e0a7fee04",
-  "linter_tag": "@0.1.24",
+  "linter_tag": "@0.1.26",
   "logging_tag": "@0.11.3+1",
   "markdown_rev": "@4aaadf3d940bb172e1f6285af4d2b1710d309982",
   "matcher_tag": "@0.12.0+2",