pgAdmin 4 commit: Fixed fatal error while launching the pgAdmin4 3.5.U

Fixed fatal error while launching the pgAdmin4 3.5. Update the version of the Flask to 0.12.4 for release. Fixes #3730

Branch
------
master

Details
-------
https://git.postgresql.org/gitweb?p=pgadmin4.git;a=commitdiff;h=b58f288eec7103aa305fa4ae012d8fbd50dbf229

Modified Files
--------------
docs/en_US/release_notes_3_5.rst | 3 ++-
requirements.txt                 | 2 +-
2 files changed, 3 insertions(+), 2 deletions(-)