docs(rtd): various cleanup

[wpbonelli]

• title was previously "Indices and tables — Flopy Documentation <version> documentation"
  • rename header in main.rst from "Indices and tables" -> "FloPy"
  • rename project from "FloPy Documentation" -> "FloPy" in conf.py
  • title will now appear simply as "FloPy — FloPy <version> documentation"
• remove the "Search page" link under "Indices and tables" section in main.rst — leads to an empty page and there is a search box in the left panel anyway
• update version in main.rst to 6.5.0.dev0 (this gets auto-updated whenever docs are built, just updating to stay current with status of develop branch)
• update copyright year in conf.py from 2022 -> 2024

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (97da396) 73.0% compared to head (6af6858) 72.9%.

Additional details and impacted files

@@            Coverage Diff            @@
##           develop   #2066     +/-   ##
=========================================
- Coverage     73.0%   72.9%   -0.1%     
=========================================
  Files          259     259             
  Lines        57887   59264   +1377     
=========================================
+ Hits         42263   43252    +989     
- Misses       15624   16012    +388     

see 78 files with indirect coverage changes