docs: Fix small documentation issues

[Dosenpfand]

Description

Fixes small issues in the documentation such as

1. Changing flask_babelpkg to flask_babel
2. Fixing typos

ADDITIONAL INFORMATION

• Has associated issue:
• Is CRUD MVC related.
• Is Auth, RBAC security related.
• Changes the security db schema.
• Introduces new feature
• Removes existing feature

[codecov]

Codecov Report

Merging #1755 (f7a6c81) into master (319b6be) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1755   +/-   ##
=======================================
  Coverage   76.88%   76.88%           
=======================================
  Files          56       56           
  Lines        8136     8136           
=======================================
  Hits         6255     6255           
  Misses       1881     1881           

Flag	Coverage Δ
python	76.88% <100.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
flask_appbuilder/security/views.py	62.16% <100.00%> (ø)

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[dpgaspar]

Thank you @Dosenpfand