travis: remove redundant go get invocations

.travis.yml

@@ -52,8 +52,6 @@ matrix:
 before_install:
  # Required for format check.
  - go get golang.org/x/tools/cmd/goimports
- # Required for code get checks.
- - go mod download gonum.org/v1/gonum || true
  # Required for imports check.
  - go get gonum.org/v1/tools/cmd/check-imports
  # Required for copyright header check.

.travis/linux/install.sh

@@ -4,13 +4,9 @@ set -ex
 # prior to more specific installation commands for a particular blas library.
 go get golang.org/x/tools/cmd/cover
 go get github.com/mattn/goveralls
-go get gonum.org/v1/gonum/blas
-go get gonum.org/v1/gonum/lapack
-go get gonum.org/v1/gonum/floats
 
 # Repositories for code generation.
 go get modernc.org/cc
-go get gonum.org/v1/netlib/internal/binding
 
 # travis compiles commands in script and then executes in bash.  By adding
 # set -e we are changing the travis build script's behavior, and the set