Add false to Redis::mget() return type

[benconda]

Summary

The functionMap entry for Redis::mget() is missing false from its return type:

'Redis::mget' => ['__benevolent<Redis|array<string, mixed>>', 'keys'=>'string[]'],

phpredis returns false on error. The false was added to mget()'s declared return type in phpredis 6.1.0:

phpredis	Redis::mget() declared return
≤ 6.0.x	Redis|array
≥ 6.1.0	Redis|array|false

This is confirmed by native reflection on a current extension (e.g. ext-redis 6.3.0):

ReflectionMethod(Redis::class, 'mget')->getReturnType()  // Redis|array|false

It is also inconsistent with the sibling entry right next to it, Redis::hMget, which already includes false:

'Redis::hMget' => ['__benevolent<Redis|array<string, mixed>|false>', 'key'=>'string', 'fields'=>'string[]'],

Effect

Before this change, PHPStan reports a === false check on an mget() result as identical.alwaysFalse ("will always evaluate to false"), and a method whose return type correctly includes false triggers return.unusedType. In practice this hides a real runtime failure mode (mget() returning false on a transport/error condition) on phpredis 6.1.0+.

Changes

• resources/functionMap.php: add false to Redis::mget(), mirroring Redis::hMget. This matches phpredis 6.1.0+ (the current line); on the older 6.0.x the extension declared Redis|array, but the functionMap targets the current extension version.
• tests/PHPStan/Analyser/nsrt/redis-mget.php: regression test asserting the return type is (array<string, mixed>|Redis|false) and narrows correctly after a === false guard. Verified the test fails without the functionMap change.