gopls: update to 0.6.5.

Show available upgrades for dependencies

gopls/v0.6.0 removed support for the code lenses that showed
available upgrades for dependencies. This behavior has now been
reintroduced, with an improved UI. Users must explicitly request
this information by clicking the "Check for upgrades" code lens
above the go.mod file's require block. Any module with available
upgrades will be highlighted with an informational diagnostic and
accepting its suggested fix will preform the upgrade.

(wiz)