tools: remove mockery from tools.go (#9196)

The `mockery` project recommends against using a binary of `mockery` that has been created using `go install`. https://github.com/vektra/mockery/pull/456. Developers of Tendermint wishing to generate mocks should avoid having a version of `mockery` on their path that does not match the version listed in  [mockery_generate.sh](https://github.com/tendermint/tendermint/blob/10e1ac8feabd8ce7fd560ebecb11b929376fcb9c/scripts/mockery_generate.sh#L11). To make this easier for developers, the `mockery_generate.sh` script uses a containerized copy of `mockery` if `mockery` is not present on the developer's `PATH`. This containerized version of `mockery` uses the same version of mockery as our CI pipelines and allows all developers to automatically use the same version without having to manage it themselves. 

#### PR checklist

- [ ] Tests written/updated, or no tests needed
- [ ] `CHANGELOG_PENDING.md` updated, or no changelog entry needed
- [ ] Updated relevant documentation (`docs/`) and code comments, or no
      documentation updates needed

scripts/mockery_generate.sh

@@ -1,15 +1,6 @@
 #!/bin/sh
 #
 # Invoke Mockery v2 to update generated mocks for the given type.
-#
-# This script runs a locally-installed "mockery" if available, otherwise it
-# runs the published Docker container. This legerdemain is so that the CI build
-# and a local build can work off the same script.
-#
-if ! which mockery ; then
-  mockery() {
-    docker run --rm -v "$PWD":/w --workdir=/w vektra/mockery:v2.12.3
-  }
-fi
 
-mockery --disable-version-string --case underscore --name "$@"
+go run github.com/vektra/mockery/v2 --disable-version-string --case underscore --name "$*"
+