fix(deps): update dependency gatsby-source-contentful to v3

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
gatsby-source-contentful	dependencies	major	2.3.56 -> 3.0.3

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Release Notes

gatsbyjs/gatsby

### [`v3.0.3`](https://togithub.com/gatsbyjs/gatsby/compare/e2605d79f3815c31c1c3458e48d15dc23256f4bd...3d8f5f18f2d55d467d7918de726daad4f3396aca) [Compare Source](https://togithub.com/gatsbyjs/gatsby/compare/9b65cbfbef6484d8750b10347bb1ef83787596c1...45f375ecb73032e0aebfa9f3f2c356ca62f1556e) ### [`v3.0.2`](https://togithub.com/gatsbyjs/gatsby/compare/84fa4be59108d02c40acbd2fb07c96a0c85aa85c...e2605d79f3815c31c1c3458e48d15dc23256f4bd) [Compare Source](https://togithub.com/gatsbyjs/gatsby/compare/c0668d4ef25dab4ac43bc3bf1064c95132c5a059...9b65cbfbef6484d8750b10347bb1ef83787596c1) ### [`v3.0.1`](https://togithub.com/gatsbyjs/gatsby/compare/bdd723e7e93fd525ea47da0d11ebb63c6edc5a35...84fa4be59108d02c40acbd2fb07c96a0c85aa85c) [Compare Source](https://togithub.com/gatsbyjs/gatsby/compare/6fe2f6a5b3c507e97c8e2fbbf6e9048d1f730b66...c0668d4ef25dab4ac43bc3bf1064c95132c5a059) ### [`v3.0.0`](https://togithub.com/gatsbyjs/gatsby/compare/e829ab9eb44e28961e9557538693fd752b221f9f...bdd723e7e93fd525ea47da0d11ebb63c6edc5a35) [Compare Source](https://togithub.com/gatsbyjs/gatsby/compare/ecc0ad37f3fb6d542964c95c2f853c25cc99d5b8...6fe2f6a5b3c507e97c8e2fbbf6e9048d1f730b66)

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