Bump league/flysystem from 1.1.3 to 2.0.5

Sourced from league/flysystem's changelog.

<h2>2.0.5 - 2021-04-11</h2> <h3>Fixed</h3>

• [AwsS3] ensure write errors are turned into exceptions.

<h2>2.0.4 - 2021-02-13</h2> <h3>Fixed</h3>

• [InMemory] Corrected how the file size is determined.

<h2>2.0.3 - 2021-02-09</h2> <h3>Fixed</h3>

• [AwsS3V3] Use the $config array during the copy operation.
• [Ftp] Close FTP connections when the object is destructed.
• [Core] Allow for an absolute root path of /.

<h2>2.0.2 - 2020-12-28</h2> <h3>Fixed</h3>

• Corrected the ignored exports for Ftp

<h2>2.0.1 - 2020-12-28</h2> <h3>Fixed</h3>

• Corrected the ignored exports for Phpseclib

<h2>2.0.0 - 2020-11-24</h2> <h3>Changed</h3>

• string type added to all visibility input

<h3>Added</h3>

• Google Cloud Storage adapter.

<h2>2.0.0-beta.3 - 2020-08-23</h2> <h3>Added</h3>

• UnableToCheckFileExistence error introduced
• Mount manager is re-introduced

<h3>Fixes</h3>

... (truncated)

• 27ea64c Pre-release changelog
• e04acf7 CS
• 83cdbf8 CS
• 06f2dcf body not bucket
• 48f1985 Don't forget to forward the call
• cb6e8ba Test failing to write a file on AWS
• 7cbbb72 Added changelog for 2.0.4
• 3a631ec InMemoryAdapter must return the number of bytes
• 97b4776 Added changelog for 2.0.3
• 4ba84a2 Added changelog for 2.0.2
• Additional commits viewable in compare view

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