fix: update Matchers type value.

[macinjoke]

I fixed this one line in index.d.ts

declare namespace jest {
-  interface Matchers<R> {
+  interface Matchers<R, T> {

Without this fix, loading both @types/jest/index.d.ts and snapshot-diff/index.d.ts will result in the following error:

ERROR in
/path/to/project/node_modules/@types/jest/index.d.ts(667,15):
TS2428: All declarations of 'Matchers' must have identical type parameters.
ERROR in
/path/to/project/node_modules/snapshot-diff/index.d.ts(13,13):
TS2428: All declarations of 'Matchers' must have identical type parameters.

Reference: DefinitelyTyped/DefinitelyTyped#39243

[thymikee]

Duplicate of #92