Update psalm/phar requirement from 6.19.* to 6.20.* - #131

src/EventLoop/Driver/UvDriver.php:164:30: MixedPropertyTypeCoercion: $this->streams expects 'array<int, resource>', parent type `non-empty-array<int, mixed|resource>` provided (see https://psalm.dev/196)

src/EventLoop/Driver/UvDriver.php:164:21: MixedAssignment: Unable to determine the type that $event is being assigned to (see https://psalm.dev/032)

src/EventLoop/Driver/UvDriver.php:162:21: MixedAssignment: Unable to determine the type that $event is being assigned to (see https://psalm.dev/032)

src/EventLoop/Driver/UvDriver.php:61:78: MixedOperand: Left operand cannot be mixed (see https://psalm.dev/059)

src/EventLoop/Driver/UvDriver.php:61:66: MixedOperand: Right operand cannot be mixed (see https://psalm.dev/059)

src/EventLoop/Driver/UvDriver.php:53:32: MixedArgument: Argument 1 of uv_poll_start cannot be mixed, expecting resource (see https://psalm.dev/030)

src/EventLoop/Driver/StreamSelectDriver.php:256:32: MixedArgumentTypeCoercion: Argument 1 of set_error_handler expects callable(int, string, string=, int=, array<array-key, mixed>=):bool|null, but parent type Closure provided (see https://psalm.dev/194)

examples/benchmark-timers-delay.php:13:29: MixedArgumentTypeCoercion: Argument 2 of Revolt\EventLoop::delay expects Closure(string):void, but parent type Closure provided (see https://psalm.dev/194)

examples/benchmark-ticks-delay.php:13:26: MixedArgumentTypeCoercion: Argument 1 of Revolt\EventLoop::defer expects Closure(string):void, but parent type Closure provided (see https://psalm.dev/194)

examples/benchmark-memory.php:28:21: MixedMethodCall: Cannot call constructor on an unknown class (see https://psalm.dev/015)

The `set-output` command is deprecated and will be disabled soon. Please upgrade to using Environment Files. For more information see: https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/