docs: refresh Go version and stability framing for v1

The quick-start guide listed Go 1.21.1 as the minimum, which has been
inaccurate since the 1.26 bump in v0.56.0. Update to match go.mod.

The contributing guide still described the project as pre-1.0 with the
"during initial development, the major version will be 0" framing. Replace
with the post-1.0 semver commitment that matches the README and migration
overview: deprecated aliases stay for the v1 line; removals defer to v2.

OSS-3453.

Author: james00012

docs/_docs/01_getting-started/quick-start.md

@@ -16,7 +16,7 @@ custom_js:
 
 Terratest uses the Go testing framework. To use Terratest, you need to install:
 
-- [Go](https://golang.org/) (requires version >=1.21.1)
+- [Go](https://golang.org/) (requires version >=1.26)
 
 ## Setting up your project
 

docs/_docs/04_community/contributing.md

@@ -256,9 +256,9 @@ go test -timeout 30m -run "<TEST_NAME>"
 This repo follows the principles of [Semantic Versioning](http://semver.org/). You can find each new release,
 along with the changelog, in the [Releases Page](https://github.com/gruntwork-io/terratest/releases).
 
-During initial development, the major version will be 0 (e.g., `0.x.y`), which indicates the code does not yet have a
-stable API. Once we hit `1.0.0`, we will make every effort to maintain a backwards compatible API and use the MAJOR,
-MINOR, and PATCH versions on each release to indicate any incompatibilities.
+Starting with `1.0.0`, breaking changes to the public API only happen in major releases. Symbols renamed or replaced
+inside the v1 line are kept as `// Deprecated:` aliases so test code that compiled against an earlier v1.x.y release
+will keep compiling against later ones; full removal is deferred to v2.
 
 ### Developing For Azure