Create routes/tenant.php only if the file does not exist

[stancl]

Fixes #187

[codecov]

Codecov Report

Merging #188 into 2.x will not change coverage.
The diff coverage is 100%.

@@            Coverage Diff            @@
##                2.x     #188   +/-   ##
=========================================
  Coverage     89.06%   89.06%           
- Complexity      314      315    +1     
=========================================
  Files            52       52           
  Lines           924      924           
=========================================
  Hits            823      823           
  Misses          101      101

Impacted Files	Coverage Δ	Complexity Δ
src/Commands/Install.php	100% <100%> (ø)	4 <0> (+1)	⬆️

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